Arsenic in Rice: Part 13 - It's There, You Just Can't See It.

Wow, 12 posts already, my, I do like to ramble.

And ramble on I will!  There is a reason for this rambling I do, and that is one of soundness.  I am calling Consumer Reports out on their recent report on arsenic they found in samples of rice they tested.  I am making a case that the amount of arsenic they found and printed in red does not warrant the use of the terms "troubling," "worrisome," "cause for concern," or "potentially harmful."

I could just stop at one post and call them a bunch of cotton-headed ninny muggins and be done with it.  And even though I would be right that there is not cause for concern, without supporting my contention, I would be no better then them.

Consumer Reports bases "troubling," "worrisome," "cause for concern," or "potentially harmful," because some rice exceeded a threshold:



For me to say there is no health concern at the maximum concentration of inorganic arsenic found, 9.6 ppb, means I have to show why Consumer Reports concern is not warranted.  The previous 12 posts have focused on what that threshold of 5 micrograms actually means in terms of risk as well as tried to show how exceeding it up to 9.6 ppb does not pose a health concern.  I tried to do this by  by showing how New Jersey came up with the number "5" and how it is dependent on a Slope Factor that most likely does not represent the true risk it theoretically calculates.

If exceeding 5 micrograms per serving is "troubling," "worrisome," "cause for concern," or "potentially harmful," then rice below that amount is not.  And if 5 micrograms is safe, then we assume a certain number of excess bladder and lung cancers is therefor acceptable.  But we can only accept those excess cancers at 5 micrograms if the Slope Factor they used actually reflects the real risk.  And when we look at the actual risk at low levels of arsenic in drinking water, the researchers find:

Since the NRC reports, a number of studies have been published that did not find an increase of internal cancers at low level arsenic exposure. These include Guo (2000), Steinmaus (2003), Lamm (2003, 2004), and Bates (2004), all of which found no evidence of an increase in bladder cancer rate at low-level arsenic exposure levels. Both Guo (2004) and Chen CL (2004) found no increase in lung cancer rate at low-level arsenic exposure levels.

Which means when Dr. Lamm reports:

• An ecologic analysis of the white male bladder cancer risk in the United States found no increase over an arsenic exposure range of 3–59 μg/L (ppb).
• Case–control bladder cancer studies found no increased risk in the United States for exposures less than 80 μg/day (ppb).

...and we take those numbers, a maximum of 59 ppb and 80 ppb, finding 9.6 micrograms in one rice serving sample will show no increased risk for bladder or lung cancer.

Dr. Lamm, Dr Honeycutt, and the National Rural Water Association lead me to conclude that the Slope Factor - used by New Jersey and the EPA in the draft IRIS document - from data presented by Morales - is incorrect and does not represent the true risk of lung and bladder cancer seen at low levels.

Not so fast, say the NRC researchers:

NRC 2001 Arsenic in Drinking Water

Which leads them to write this:

NRC 2001 Arsenic in Drinking Water

So you mean to tell me that you can calculate the risk from data collected for "Liver, lung, and bladder cancer mortality data [that was] collected from death certificates of residents in 42 villages during 1973 through 1986"....

....And you can make a Slope Factor based on arsenic concentrations in the drinking water wells "collected from wells in the 42 villages between 1964 and 1966" (1)....

...And then you tell me that you cannot calculate the low level risk from the current data available in the US because of "unknown distribution of other risk factors?"

Really?  Tell them what I think about that Col Potter:















Here is what Dr. Lamm points out:

If an ecological study in the range of interest is desired, then the data are available for analysis from US government sources. These data would obviate the need to make speculative assumptions of differences in body weight, fluid consumption, nutritional status, etc. between the study population and the US population.

And here is what the EPA is concluding should be the Slope Factor and risk for arsenic

EPA IRIS

At that Slope Factor, we would expect to see 7.3 excess cancers in 1000 (7.3E-03).

Dr. Honeycutt with the TCEQ says "horse hockey" as well:

For bladder cancer alone, the incidence risk calculated by USEPA based on final draft values for males/females is 3.1E-04 per μg/L. Therefore, based on 2 μg/L as an average drinking water concentration, the estimated bladder cancer risk for the US population would be 6.2 per 10,000 or 62 per 100,000. However, the actual occurrence of bladder cancer in the US is about 23 cases per 100,000 (males/females combined). It would take 3 times the actual bladder cancer incidence for US males/females combined to even make possible the 62 cases per 100,000 estimated due to arsenic exposure from drinking water alone. Thus, the incidence risk calculated by USEPA final draft values for bladder cancer appears to be inaccurate and overly conservative.

Okay, so I have beat the hell out of this dead horse on Slope Factor.

If I have not supported by argument that the Slope Factor is incorrect, and, therefore the 5 ppb is incorrect, there is not more evidence I can offer.  I can say, based on what I have shown in these previous 13 posts, that rice that may go as high as 9.6 μg per serving is not "troubling," "worrisome," "cause for concern," or "potentially harmful."  It is just rice.

I have also concluded this as well about how a Slope Factor for cancer risk is calculated:

The ability to fit a line through data points does not necessarily mean that the underlying data adequately define the shape of the dose-response curve, including the critical low dose region.
(Honeycutt TCEQ)

Next Post: Arsenic in Rice:  Part 14 - Give me a "P"...Arsenic in the Urine

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Arsenic in Rice: Part 12 - Look No Closer Than Your Own Backyard

The real problem with Consumer Reports articles on arsenic in apple juice and rice is that it shows concentrations of arsenic that are not "troubling," "worrisome," "cause for concern," or "potentially harmful."

The rice report, specifically, conveys to the public that there is a risk by showing rice samples with arsenic concentrations printed in red.  This table of inorganic arsenic they found in the rice they samples is explained like this::

What message does Consumer Reports want their readers to leave with?  Should they stop consuming rice? Buy only brands without out the "red" numbers?  Throw out the rice they have in their pantries?  What should be done?

What, other than "troubling," "worrisome," "cause for concern," or "potentially harmful," will the average reader conclude when looking at those results?

This is the problem with a threshold.  Safe on one side, unsafe on the other.  What Consumer Reports and their experts are either woefully ignorant of, or are be purposely misleading, is that the New Jersey threshold of 5 ppb does not in itself mean "safe" nor does exceeding it by twice the amount, in this case 9.6 ppb (the maximum inorganic arsenic Consumer Reports detected) mean "unsafe."

That 5 ppb "limit" is nothing more than a number New Jersey wants based on the Slope Factor that shows a one in one million excess bladder/lung cancer risk of 0.003 ppb.

My point - and maybe i made it long ago - is that 5 ppb is just a number that can be obtained, it is not a number that exceeding it is "troubling," "worrisome," "cause for concern," or "potentially harmful."  It came about from a Slope Factor based on data from an ecological study from a high exposure population in Taiwan.

The Taiwanese dataset [data underlying the study Wu et al. (1989) study and the analyses in Morales et al. (2000)] has been analyzed by the NRC (1999; 2001) and the EPA]. It has served as their analytic database for estimating the risk of internal cancers from the ingestion of water containing inorganic arsenic. NRC considered that the reason for modeling with the SW-Taiwan data was that at that time there was insufficient information to assess the risk from low-level exposure and only the SW-Taiwan study had a sufficient quantity of data over a wide range of arsenic exposures that could be used for risk analysis and extrapolation. (Lamm 2005)

That same dataset is also being used EPA to lower the MCL of arsenic to 3 ppb, and it is based on the Slope Factor derived from that data.  That Slope Factor, the one that leads Consumer Reports to 5 ppb "limit" and is sending the EPA towards a 3 ppb limit, is being questioned as to its validity and the potential damage it will cause if it is adopted if it is indeed incorrect.  As Dr. Honeycutt with the TCEQ tells the EPA:

Proceeding with this SFo will unnecessarily alarm the public by giving a greater perception of harm and risk than is actually taking place.

Dr. Honeycut is not the only one who takes issue with the draft IRIS report and the Slope Factor derived from the Taiwanese dataset.  Here is what the National Rural Water Association wrote about this draft IRIS report:

High quality data from the US and elsewhere indicate much lower risks from iAs ingestion at the levels of exposure relevant for the past and current MCL, yet these studies are not used at all in the Agency’s new quantitative risk assessment because EPA focuses exclusively on the Taiwanese data.  

I know what you may be thinking: Well of course those two are opposed to a lower standard!  It's going to cost them money and effort!  Yeah, that could be the driver, but in the end, is what they are saying, their "point" sound?  Heck, even though I have no dog in this hunt, I have used 12 posts to support my point, and I got a lot more support I am going to throw out there.

Okay, so I'll give you the bias angle, is there anyone else that takes issue with the EPA and the dataset used to determine the Slope Factor?

Well I found something written by this guy named Steven H. Lamm.  He is an MD and an MPH (like me) and bills himself as a "Consultants in Epidemiology & Occupational Health, LLC. with Johns Hopkins University-Bloomberg School of Public Health Georgetown University School of Medicine."

I found a letter from him to the EPA Science Advisory Board (SAB), dated September 5, 2005.  He writes:

There are many questions regarding data quality that are raised by the above analysis. Are the diagnoses correct? Is the case count correct? Is the population ascertainment and subsequent person-year distributions correct? Is the well inventory complete and accurate? Are the arsenic measurements correct? Did the residents only drink from their village wells? Was the arsenic level constant over decades? Were the risks independent of subsequent switch to piped water both quantitatively and temporally?

What becomes troubling about the Slope Factor the EPA wants to use is that they seem to be ignoring this:

As the data to examine these questions is limited or absent, we have to accept various assumptions. We are struck with the observation that in multiple ways when the data is bifurcated, the dose-relationship differs in the two sections. We conclude that there exists within the data some additional unobserved factor(s) that influences the outcome, but has not been adequately identified or characterized. Lamm

And now the plot thickens.  Remember how the Rural Water guys said "High quality data from the US and elsewhere indicate much lower risks from iAs ingestion at the levels of exposure relevant for the past and current MCL?"  Well here is what Lamm reports to the EPA - using the same data used by the EPA:

We noted that the lower level exposure villages showed a negative slope with R2 = 0.25, which appears to be inconsistent with the general expectation of a dose-response model, though p=0.10.

The SW-Taiwan dataset reflects significant inherent geographically-based risk factor(s) which, when disentangled, reveal no significant arsenic-dependent risk for bladder and lung cancers for the low-level exposure villages.

"Disentangled,"  hehe, MPH's use funny words.

Well now...where does all this lead us?  Dr. Honeycutt complains about the noise, Dr. Lamm says the lower dose-level exposed Taiwan villagers reveal "no significant arsenic-dependent risk for bladder and lung cancers," and The National Rural Water folks wonder why the EPA is not looking at "data from the US and elsewhere indicate much lower risks from iAs ingestion at the levels of exposure relevant for the past and current MCL."

That's a good question, that last one.  Why don't we look at US exposure to arsenic and compare bladder & lung cancer incidence based on exposure?  I mean, to me, that would show if these low levels of arsenic actually do present the same degree of risk the EPA's new Slope Factor is predicting.

I mean, wouldn't current data using American's with American habits and American data on cancer make a much better study group?  Has that been looked at?  Why yes, yes it has.  According to Dr. Lamm in Environmental Health Perspectives 2006 July; 114(7): 1077–1082:

• An ecologic analysis of the white male bladder cancer risk in the United States found no increase over an arsenic exposure range of 3–59 μg/L (Lamm et al. 2004). 
• Case–control bladder cancer studies found no increased risk in the United States for exposures < 80 μg/day (Steinmaus et al. 2003)

Interesting...

Dr. Lamm finds:

• A threshold-like model indicating that the bladder cancer mortality risk does not increase with exposure levels < 150 μg/L is consistent with other epidemiologic data.
•  Cigarette smoking still remains a risk factor for bladder cancer.

So here is my take on this.  We have really, really good data on the arsenic concentration in water that is consumed.  For example:

Evaluation of Arsenic Contamination in Texas

...and we have really, really, good data on cancer

Source

So putting the two together, me thinks we would see elevated incidence of bladder and lung cancer in areas where the arsenic is highest and less in areas where the arsenic is low.  At least that data would be newer and more complete and any confounders present would be relatively the same as in Taiwan.

Makes sense to me to look here as well as there.


Arsenic in Rice: Part 13 - It's There, You Just Can't See It.

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Arsenic in Rice: Part 11 - Dose-response is the cornerstone of toxicology

From 2010 Draft IRIS we learn:

In response to comments from NRC and SAB, a slightly different approach to estimate cancer risks for U.S. populations is being used. In the following analysis, arsenic concentrations corresponding to an additional 1% lifetime cancer incidence (effective dose; ED01 values) above “background” are derived for each endpoint [bladder/lung cancer].

A little primer on EDs...

NRC

 Using the Morales et al. data, the EPA IRIS reports:

Depending on the model used and the comparison population used in the analysis, the effective dose at the 1% level (ED01) estimates ranged from 21 to 633 ppb for male bladder cancer, and from 17 to 365 ppb for female bladder cancer. The lung cancer risk for males was found to be slightly higher than the bladder cancer risk, with ED01 estimates ranging from 10 to 364 ppb.  The risk for female cancer tended to be higher than that of males for each cancer type. For lung cancer, female ED01 estimates ranged from 8 to 396 ppb.

What this means is that the concentration required to obtain an additional 1% cancer incidence for male bladder cancer is either 21 ppb or 633 ppb, depending on what model you use.

Why this is important, this variation of 21 or 633 needed to get the same result - an additional 1% cancer incidence for male bladder cancer, shows up here (draft IRIS):

Also derived are lowest effective dose (LED01) values, which represent the lower confidence limits on the dose corresponding to a one percent lifetime incidence risk in the U.S. population.  [R]isk estimates are derived based on a linear extrapolation from the points of departure (LED01s for lung, bladder, and combined cancers) because the [Mode of Action] MOA for inorganic arsenic is unknown.

What this means, if I am understanding it correctly, is that depending on what model is used, an ED01 is produced.  This ED01 is a statistically derived number and will have a 95% Confidence Interval produced, and the lowest number of that range will produce the LED01.  That number is what is used to produce the Slope Factor which is used to produce the risk of excess cancers which is then used to determine the "safe" dose - the line in the sand - the threshold.

You can see these values, the ED01 and LED01, in Table 5-3:

Draft IRIS Page 131

I can't really do the math here any justice, but what you can see from this table is that the LED01, which is the lower confidence interval, and is used to produce the line (linear extrapolation) from which the Slope Factor is determined, which represents the theoretical potency, which determines the risk (1 in 1,000,000 or 1, 10,000) was based on the lower values spat out by the different models used to calculate the ED01.

...in the house that Jack built!

Confused?  Me too, kind of.  What this shows is that when calculating the Slope Factor the lowest concentrations of arsenic that showed came out of the models were used.  This being the case, with a range of ED01 anywhere from 21 ppb or 633 ppb, for example, means that the risk calculated from these Slope Factors are extremely high.  With that in mind, a serving of rice that has inorganic arsenic 5 ppb over the 5 ppb threshold established by New Jersey is probably no more hazardous for lung/bladder cancer than if it was 5 ppb below that value.

Because the Slope Factor is dependent on a linear extrapolation of the LED01 the numbers used to calculate the ED01 must accurately reflect an additional 1% lifetime cancer incidence above “background.”  

EPA reports in the draft IRIS that these numbers were from 21 ppb or 633 ppb for male bladder cancer depending on what model was chosen.  How far of, then, the Slope Factors are from reality (actual incidence of excess bladder/lung cancer) is anyone's guess.

What there is no guessing about is this.  Eating a serving of rice containing 9.6 μg every day - for 70 years - would not be "troubling," "worrisome," "cause for concern," or "potentially harmful."

But don't take my word for it.  Let's look at what the National Rural Water Association wrote about this draft IRIS report:

The most likely  [Mode of Action] MOA for arsenic correspond to sublinear dose-response models, which when fitted to the available data, suggest much lower cancer risks (by a factor of up to 200) at exposure levels at or below the MCL when contrasted to the EPA’s estimates from the linear model.

..and:

Since the MOA could not be established, the EPA is continuing in its application of the linearized, non-threshold model of dose-response, despite a lack of evidence of increased cancer incidence at typical environmental levels of exposure in the U.S.

...and:

The data of Morales et al. for bladder cancer in a Taiwanese population has been graphed. The arsenic concentration is in μg/L, and the y-axis is lifetime probability of bladder cancer. The solid line is the best-fitting linear model::

Which brings us back to Dr. Honeycutt with the TCEQ:

USEPA used lung and bladder mortality data from Morales et al. (2000) for the dose-response assessment for the final draft SFo.  Morales et al. (2000) uses these mortality data to calculate standardized mortality ratios (SMRs) and notes,

• “Although the computed SMRs display a large amount of noise, there appear to be higher SMRs at high exposure levels compared to exposures in the lower range, especially for bladder and lung cancer.”

Dr. Honeycutt responds:

To say that there is “noise” in the SMRs over the eight exposure categories is an understatement. 

Dose-response is the cornerstone of toxicology, but the lung and bladder mortality data (SMRs) from Morales et al. provide a poor basis for dose-response assessment as a dose-response is not apparent and not monotonic. 

Breaking the data down into the form of age-specific person-years at risk and cancer deaths does not improve the basis for dose-response assessment; it only obscures the lack of a good dose-response which is readily apparent from examination of the SMRs.

I have whipped this dead horse on the Slope Factor as much as I can.  Let's look at it another way.  Do we see the number of bladder cancers estimated by the Slope Factor derived from the Morales et al. data?

I addressed this once before in a previous post.  I'll do it again with a bit of a different spin.

Next Post: Arsenic in Rice: Part 12 - Look No Closer Than Your Own Backyard

Arsenic in Rice: Part 10 - Everyone loves Morales et al.

In my last post, I wrote that eating one serving of rice containing 9.6 μg of inorganic arsenic - every day - for 70 years - would present a risk of 7 in 1,000 excess bladder/lung deaths for females.  This, I wrote,  was 3 excess bladder/lung cancers more than what the "most protective level" of 5 μg/L would theoretically produce.

I want to be clear here and make sure that my point is not being misconstrued.  I am not making the point that 5 μg is not the "most protective level" and that it should be lower, say 0.003 μg/L.  On the contrary, what I am trying to get across is that 5 μg/L is not an appropriate number to establish a threshold.  Not because it is too high, but because it does not imply "safe" and "unsafe" like Consumer Reports and their experts are wanting us to conclude.

That number -  5 μg/L - is just a number to support getting the arsenic concentration down as low as we can to the stated goal of "zero."  If we understand environmental causes of cancer correctly, then anything above zero is a risk.  This does not have to paint us into a corner, but it does.

Why?  Because Consumer Reports implies that a serving of rice exceeding 5 μg/L is "troubling," "worrisome," "cause for concern," or "potentially harmful."  They assume that 5 ppb is "safe" and that above that is "unsafe."

"Troubling," "worrisome," "cause for concern," or "potentially harmful," was used by Consumer Reports to convey "unsafe" for two reasons in my opinion:

1. They do not understand what New Jersey's 5 μg/L arsenic in drinking water represents, and;
2. They are pushing a zero threshold agenda

Again, so that my message is not misconstrued:

If Consumer Reports considers New Jersey's arsenic standard of 5 μg/L the "safe" threshold for rice....and;

Rice that has up to 5 μg/L of inorganic arsenic per serving would not make it "troubling," "worrisome," "cause for concern," or "potentially harmful."....and;

New Jersey considers 5 μg/L to be the "most protective level"...and;

Based on the EPA Oral Slope Factor derived from data produced by Morales et al,  5 μg/L would result in a risk of 3.6 excess bladder/lung cancers in 1,000....

Then Consumer Reports agrees that a risk of 3.6 out of 1,000 excess bladder/lung cancers is most protective of the population that consumes one serving of rice per day for 70 year.

You can see why I take issue with the conclusions presented by Consumer Reports and the experts.  They imply that on this side it is "safe" and on that side it is "unsafe."  It is neither.  Which is why using an MCL should never be used to present to the public a comparison of the ranges where the MCL is exceeded.

Consumer Reports is wrong, wrong, wrong, on this.  It does not provide a "yardstick" - it provides the public nothing but confusion and concern.  Which is exactly the point Dr. Honeycutt with the TCEQ was driving at:

Proceeding with this SFo [Oral Cancer Slope Factor from Morales et al.] will unnecessarily alarm the public by giving a greater perception of harm and risk than is actually taking place.

By using red ink in their tables, as well as using the terms "troubling," "worrisome," "cause for concern," or "potentially harmful," Consumer Reports has alarmed the public by supporting a greater perception of harm and risk than is actually taking place.  This is inexcusable for a magazine of this caliber and extremely unsettling that their toxicological experts were not knowledgeable of this fact.

So let's get back to it shall we.  Is inorganic arsenic in a serving of rice that is greater than 5-ppb but less than 10 ppb "troubling," "worrisome," "cause for concern," or "potentially harmful?"

Only is you think an increase of risk from 3.6 in 1,000 to 7 in 1,000 is substantial enough.  And that increase is also dependent on consuming a serving of rice each day for 70 years with 9.6-ppb inorganic arsenic (we will ignore for now the fact that the average concentration of arsenic found in all the samples was below 5 ppb and assume that each day the rice contains the maximum level found - 9.6 ppb).  Oh, and another thing we need to consider is that the risk, from 3.6 to 7, is dependent on the Oral Slope Factor that was developed using data from Morales et al. (2000).

Let's look at that Morales et al. data, shall we?  First off, I am not trying to make a case that the data is - or is not - valid.  I will assume it is.  What I want to show is how much uncertainty there is in the final Oral Slope Factor that was calculated.  This uncertainty makes the increase in risk from 5-ppb to 10-ppb impossible to calculate with any degree of accuracy.  Yet, there it is, used by Consumer Reports to draw a line in the sand, a threshold held up as sacrosanct.

Here is what the EPA has to say about the data they used from Morales et al.:

The calculation of cancer risks from the Taiwanese epidemiological data was performed using Excel workbook files. The files contained the input data for the dose-response models and spreadsheets to accept user-specified inputs, perform calculations, and summarize outputs from the assessment. Input data included male and female lung and bladder cancer mortality and person-years at risk (PYR) data for arsenic-exposed populations from 42 villages obtained from Morales et al. (2000), village water arsenic concentrations (minimum, median, and maximum data sets), and southwest Taiwan and all Taiwan reference population mortality and PYR data.

You can download those Excel files here.  Digging a bit deeper, we get this from the EPA in the IRIS draft report:

The Morales et al. (2000) ecological investigation re-analyzed data originally reported by Chen et al. (1988a, 1992) and Wu et al. (1989) from 42 villages in the arseniasis-endemic region of southwestern Taiwan by considering the number of liver, lung, and bladder cancer deaths.  Morales et al. (2000) used a generalized linear model (i.e., Poisson distribution) and the multistage-Weibull models to determine lifetime cancer risk estimates. Liver, lung, and bladder cancer mortality data were collected from death certificates of residents in 42 villages during 1973 through 1986.

Okay, they collected data from death certificates...

Drinking water samples had been collected from wells in the 42 villages between 1964 and 1966.

...and Morales et al. used sample data from 1964 through 1965.  Well...okay...

SMRs [standard mortality ratio] were used to summarize the observed patterns of mortality in the collected data. Morales et al. (2000) selected two comparison populations (the Taiwanese population as a whole and a population from a southwestern region of Taiwan) to account for urban versus non-urban populations differences.

...okay...standard toxicological stuff...

Although a non-significant trend was observed in the combined cancer analyses with respect to age, there was no observed tendency in liver, lung, or bladder SMRs with respect to age. This suggests that there is no age dependency on the risk ratio.

...okay, that takes out one confounding issue...

The Morales et al. (2000) investigation results showed that exposure-response assessments were highly dependent on the choice of the analysis model and whether or not a comparison population is used in the analysis.

And the reason?....

One possible explanation for this observation is the inherent uncertainty associated with the limitations of an ecological study design. Depending on the model used and the comparison population used in the analysis, the effective dose at the 1% level (ED01) estimates ranged from 21 to 633 ppb for male bladder cancer, and from 17 to 365 ppb for female bladder cancer. The lung cancer risk for males was found to be slightly higher than the bladder cancer risk, with ED01 estimates ranging from 10 to 364 ppb. The risk for female cancer tended to be higher than that of males for each cancer type. For lung cancer, female ED01 estimates ranged from 8 to 396 ppb.

Wait...the number used to calculate the Slope Factor is based on the 1% effective dose (ED)...and that number ranges from 21 to 633 ppb, 17 to 365 ppb, 10 to 364 ppb, and 8 to 396 ppb for the two cancers in men and woman?

And they calculated a Slope Factor that was used to support a standard of 5 ppb for arsenic in drinking water.  And Consumer Reports wants me to believe that exceeding 5 ppb up to a maximum of 10 ppb in a serving of rice is "troubling," "worrisome," "cause for concern," or "potentially harmful?"

Really...are you serious Consumer Reports?  You are basing it on a threshold for arsenic in drinking water that uses data with this in play:

Weaknesses include the ecological study design (i.e., there were no individual monitoring data and individual exposures were not available) and the fact that potential confounders such as smoking, dietary arsenic, and the use of bottled water (U.S. population) were not controlled for in the analysis.

And in spite of these weaknesses, the EPA and New Jersey, and the NRC marched forward with a Slope Factor.  Which is exactly why Dr. Honeycutt with the TCEQ made this statement:

Proceeding with this SFo will unnecessarily alarm the public by giving a greater perception of harm and risk than is actually taking place.

So how "off" can this excess cancer risk be?  Glad you asked that, now I can move on to the 11th post.


Next post:  Arsenic in Rice: Part 11 - Dose-response is the cornerstone of toxicology

Arsenic in Rice: Part 9 - The Broad Shoulders of Morales et al.

Consumer Reports has drawn a line in the sand regarding the amount of inorganic arsenic they found in a bunch of different rice samples they collected and analysed.

Consumer Reports uses the New Jersey threshold - MCL - for water, 5 μg/L.  That threshold was based on analysis by the NRC on data proved by Morales et al.

Morales, KH; Ryan, L; Kuo, T-L; et al. (2000) Risk of internal cancers from arsenic in drinking water. Environ Health Perspect 108:655–661.

5 μg/l was what the EPA originally proposed an arsenic standard but in January 2001, it was changed to 10 μg/l.  The consensus of EPA, was to get the MCL down to 5 μg/L.  Enter a new President and a new director of the EPA, and in 2010,  IRIS issues an "External Review Draft" called the "Toxicological Review of Inorganic Arsenic (Cancer).  It is important to not here, that this draft has been in the making since 1999.  A different administration views the risk differently.  Which is one of my points.  How should we quantify risk for water and rice that is reasonable, prudent, and...well...reflects reality.

These cancer risks are based on a Slope Factor, which is "the theoretical cancer potency estimate for humans." (CalEPA)

I'm going to argue that this "theoretical cancer potency estimate" paints us into a corner when attempting to communicate the risk of exposure, especially the risk to a chemical suspected of causing cancer in humans.

It is not that it is "theoretical" that I take issue with, it is that the number it derives - the excess cancer risk - is not a threshold whereby exceeding it by 1, 5, or 10 ppb becomes "troubling," "worrisome," "cause for concern," or "potentially harmful" as Consumer Reports points out that it does.

If I am going to support my conclusion that the rice is "safe," I am going to have to show why exceeding the 5 ppb threshold is not harmful.  The thing is, I can't do that.  I have been painted into a corner that says there is no safe exposure to a carcinogen.  This corner is also where New Jersey finds itself when it says the drinking water concentration that results in a one-in-one-million excess lifetime risk meets their law as an acceptable risk.

This corner gives us no where to go based on this thinking.  This is why Dr. Honnycutt with the Texas Commission on Environmental Quality made this statement to the EPA about their 2010 External Review Draft on the  "Toxicological Review of Inorganic Arsenic (Cancer)."

Like I said previously in my past posts, exceeding 0.003 μg/L increases the risk.  Accepting the threshold of 5 μg/L as the "most protective level" assumes that one then accepts a new risk threshold of 2 excess cancers per 1,000 (2E-03) based on consuming two (2) liters of water at 5 μg/L.  This is based on a Slope Factor that I calculated based on a 1 in 1,000,000 risk at 0,003 μg/L (I assumed 2 liter/day).

Let's instead look at the risk using the new and improved draft IRIS values, which are based on an Oral Cancer Slope Factor for women:

2010 Draft IRIS Page 150-151

Based on the IRIS data, which is based on data from Morales et al. (2000), drinking on liter of water, or consuming one serving of rice (Consumer Reports) with 0.14 μg/L (ppb)  would present an excess cancer risk for lung and bladder in women of 1 in 10,000 (10-4, the acceptable risk for carcinogens in water.)

Using that same data, consuming one serving of rice that had the highest concentration of inorganic arsenic (9.6 μg)  for a lifetime - 70 years- would see an excess cancer risk of  7.3 in 1,000 in women.

Looking at it another way, if the "unit risk" for arsenic is 7.3 in 10,000 for one μg of arsenic in water, 10 μg would increase that risk 10-fold - 73 in 10,000 or 7.3 in 1,000.

If we can accept that unit risk, which was derived from data provided by Morales et al. (2000), then we can figure out what the excess cancer risk is at New Jersey's "most protective level" of 5 μg/L:
5 μg/L x 7.3E-04 = 36.5E-04 or 3.6 in 1,000.

Now we can have some fun....

According to Consumer Reports:

Using the 5-ppb standard in our study, we found that a single serving of some rices could give an average adult almost one and a half times the inorganic arsenic he or she would get from a whole day’s consumption of water, about 1 liter.

Therefore, one serving of rice that contained the maximum concentration of inorganic arsenic detected, 9.6 μg:

...would present a risk of 7 in 1,000 excess bladder/lung deaths for females - which is 3 excess bladder/lung cancers than what the "most protective level" of 5 μg would theoretically produce.  This is all based on the following assumptions:

• The female weighs 70 kg.
• The female eats one serving of rice containing 9.6 μg inorganic arsenic - every day - for 70 years.
• The female gets bladder or lung cancer.
• The female dies from bladder or lung cancer.

All of those assumptions must be met to get an excess cancer risk of 7 in 1,000.  If she was to consume one serving of rice were with 5 μg of inorganic arsenic - every day - for 70 years, we would see an excess cancer risk of 3.6 in 1,000 which Consumer Reports tells us is at the "most protective level."

And, even if all of those assumptions play out, that excess cancer risk is dependent on a Slope Factor that was developed from data produced by Morales et al.


Next post: Arsenic in Rice: Part 10 - Everyone loves Morales et al.


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Arsenic in Rice: Part 8 - How Low Can You Go?

Consumer Reports implies that rice above a 5 ppb standard poses a "troubling," "worrisome," "cause for concern," or "potentially harmful"situation for those who eat it.

Using the 5-ppb standard in our study, we found that a single serving of some rices could give an average adult almost one and a half times the inorganic arsenic he or she would get from a whole day’s consumption of water, about 1 liter.

That threshold of "5-ppb" came from New Jersey:

[t]he 5 μg/l arsenic MCL [was selected] after consideration of the findings and recommendation of the New Jersey Drinking Water Quality Institute (Institute). The Institute reviewed the reports issued by the National Academy of Sciences (NAS) on the health effects of arsenic in drinking water in 1999, as well as an update of this report released in 2001 (Arsenic in Drinking Water: 2001 Update, NAS Press, 2001).  Based on the current NAS analysis, the Institute determined that the drinking water concentration that results in a one-in-one-million excess lifetime risk of lung and bladder cancer for United States populations was an estimated 0.003 μg/l (or three nanograms per liter or three parts per trillion).

Therefore, in view of its concerns regarding reliable removal technology, the [New Jersey Department of Environmental Protection] determined to promulgate the arsenic MCL at 5 μg/l. This determination comports with the NJSDWA mandate to establish the MCL at the most protective level within the constraints of medical, scientific and technological feasibility.

Even at that, some folks, like Jeffrey H. Tittle with the Sierra Club were not happy:

Source

How New Jersey got to "5-ppb" is important because it is what Consumer Reports uses to inform their readers that rice samples found with inorganic arsenic over that threshold of "5-ppb" is "troubling," "worrisome," "cause for concern," or "potentially harmful."  If 5-ppb is okay for Consumer Reports and is implied to be "safe," they are telling the Sierra Club that 3-ppb is too low.  But I digress....

5-ppb, which is 5 μg/l, was the amount settled on because a water system cannot effectively treat water to get the arsenic down below 5 ppb.  If you cannot treat it to less than 5 ppb, then all water systems with arsenic above 3 ppb would be in violation.  Even though the Sierra Club and the NJ Institute believe 3 ppb should be the standard, that unfortunate little devil called "reality" steps in and tells them that you can't always get what you want.

The point here is this:  5 ppb or 3 ppb is not the number that will get you to what New Jersey's law wants - which is an excess cancer risk of one in one million.  To get to that risk level, 1 in 1,000,000 the water must have an inorganic arsenic concentration of  "0.003 μg/l (or three nanograms per liter or three parts per trillion)."

My point is that none of these numbers, 5 μg/l, 3 μg/l, or 0.003 μg/l, are thresholds to which exceeding them by up to 5 ppb would be "troubling," "worrisome," "cause for concern," or "potentially harmful," as Consumer Reports tells its readers.

So lets look at just how conclusive that number of 0.003 μg/l (or three nanograms per liter or three parts per trillion) is.  That number presents an acceptable risk on one excess bladder/lung cancer per 1,000,000.  Basically anything above 0.003 μg/l increases the risk.  When, I will ask, does that increase start to meet the Consumer Reports designation of "troubling," "worrisome," "cause for concern," or "potentially harmful?"

New Jersey came up with the Slope Factor that produced 0.003 μg/l,using the research performed by the National Academy of Sciences (NAS) who put forth the NRC report,  In the NRC report we learn:

Because the EPA did not present theoretical lifetime excess bladder and lung cancer risk estimates [in 2000], the [NAS] used linear extrapolation from the EDs [1% Effective Dose's] presented in Morales et al. (2000) to estimate these risks at 3, 5, 10. and 20 μg/l .

So here we are in 2012.  New Jersey settled on 5 μg/l, they proposed 3 μg/l which would have made the Sierra Club happy, but REALLY wanted 0.003 μg/l.  The EPA, on the other hand, came up with an MCL of 10 μg/l and an MCLG of zero.

So many numbers, so many choices of "safe."

And when you look at how those numbers were derived, one thing starts to pop out at you (well at me anyway).  That is, there is a connection that binds them all:

After the publication of the proposed rule, Morales et al. (2000) published a study in which a risk assessment for mortality from several internal cancers was presented.  The risk assessment was based on reanalyses of the data from southwestern Taiwan.  Risk estimates were calculated for mortality from lung, bladder, and liver cancers, as well as combined cancer deaths, using 10 different statistical models, calculated with and without a Taiwanese comparison population.  [NRC]

Which then tells us this:

EPA was considering those analysis in the final rule making [that established the current 10] and, therefore, published a Notice of Data Availability in the Federal Register summarizing and further analyzing the information from Morales et al. [NRC]

Which leads to the EPA producing a draft document in 2010 called the "IRIS Toxicological Review of Inorganic Arsenic (Cancer)" where we learn this:

In the course of this analysis, EPA has investigated the impact of alternative model forms on the cancer risks estimated for the Taiwanese and U.S. populations for individual endpoints (lung and bladder cancer). Based on the past experience of Morales et al. (2000) and modeling results presented by NRC (2001), this effort was limited to exploring alternative forms for the dose dependence of risks.

These MCLs, these thresholds for what is "safe," are the result of a Slope Factor that is used to estimate excess cancer risk from inorganic arsenic that was derived this way:

EPA investigated a range of model forms for use in the risk assessment, building on previous efforts, including U.S. EPA (2001) and Morales et al. (2000).  The model used in the derivation of the preferred risk assessments employs:

• Poisson regression (of cancer mortality against age and dose) fit by maximum likelihood estimation (MLE).
• A quadratic age model.
• A linear multiplicative dose term.
• Confidence limits on the dose term estimated by profile likelihood.
• Estimates derived for the data set that includes the southwest Taiwan reference population.

That's complicated toxicologist talk.  What I want to focus on is that all of these numbers are based on a Slope Factor that comes from data provided by some guy named "Morales" and his friends "et al."

Morales...Morales...Morales...

Next Post: Arsenic in Rice:  Part 9 - The Broad Shoulders of Morales et al.

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Arsenic in Rice: Part 7 - EPA and IRIS

So what do we know so far...

• Consumer Reports compares the amount of arsenic found in rice to the New Jersey threshold for arsenic in drinking water.
• New Jersey set its arsenic level based on the "limits of medical, scientific and technological feasibility."
• The New Jersey limit is based on data presented in the National Academy of Sciences (NAS) report titled Arsenic in Drinking Water: 2001 Update
• The NAS report is based on a health risk assessment performed by the EPA in 1996.
• The EPA had proposed an arsenic standard for drinking water of 5 μg/l
• The EPA set an MCL standard of 10 μg/L on January 22. 2001 based on dose-response models and extrapolation from a cancer study of Taiwanese population exposed to high concentrations of arsenic in its drinking water.

We went from a proposed threshold of 5 μg/L to a threshold of 10 μg/L.  New Jersey, in 2004 takes that information and ends up back at 5 μg/L. Interesting...

Which brings us to present time.  February 19, 2010 EPA places in the Federal Register a notice for public comment the "2010 draft document titled, Toxicological Review of Inorganic Arsenic: In Support of the Summary Information on the Integrated Risk Information System (IRIS)":

The purpose of this Toxicological Review is to provide scientific support and rationale for the hazard and dose-response assessment in IRIS pertaining to chronic exposure to inorganic arsenic.

In the document, the EPA states:

Quantitative risk estimates may be derived from the application of a low-dose extrapolation procedure. If derived, the oral cancer CSF (CSF) is a plausible upper bound on the estimate of risk per mg/kg-day of oral exposure.

 Heading on down to page 151, I read, in bold print, this:

In keeping with EPA policy, the combined oral CSF for women (25.7 per mg/kg-day) is appropriate for use in establishing health criteria, since, based on the available data, women appear to be the more sensitive group.

Wow, that's a significant difference in the Slope Factor New Jersey used which was 11.6 mg/kg-day.  At that Slope Factor, New Jersey determined that the drinking water concentration that results in a one-in-one-million excess lifetime risk of lung and bladder cancer for United States populations was an estimated 0.003 μg/L (or three nanograms per liter or three parts per trillion).

With a Slope Factor of 25.7 per mg/kg-day that estimated μg/L will be even lower.  So lets look at estimating what exactly that risk would be.  I'll use the IRIS calculation for that:

IRIS - Draft

With that formula in Equation 5-4, we can calculate the excess risk for one μg/L of arsenic at a Slope Factor of 25.7 per mg/kg-day.

25.7 x 0.001 x (1 / 70) = 3.67 excess cancers in 10,000 per μg/L of arsenic.

Let's put this into play.  If Consumer Reports believes that exceeding 5 ppb of arsenic is "troubling," "worrisome," "cause for concern," or "potentially harmful," then the risk they are assuming what is "safe" will present a risk of  8 excess bladder and lung cancers per 10,000 if the Slope Factor is 11.6 mg/kg-day as New Jersey used.

If the 2010 EPA IRIS Slope Factor of 25.7 mg/kg-day is used, 5 ppb would present a risk of  2 excess bladder cancers per 1,000.

You should start to see the problem we produce when we draw a line in the sand and claim "safe" on this side and "troubling," "worrisome," "cause for concern," or "potentially harmful," on the other.  It is only safe if the starting point for where "safe" begins is agreed upon.

Because Consumer Reports is using 5 ppb based on the New Jersey standard, it is claiming that "safe" means no more than 8 excess bladder and lung cancers per 10,000.  If New Jersey was wrong, and the EPA is correct, what Consumer Reports considers "safe" is now 2 excess bladder cancers per 1,000.

If you think about it, that number "5" does not really mean "safe" anyway - nor does it mean "troubling," "worrisome," "cause for concern," or "potentially harmful."  It is a theoretical number based on a model that spits out a value we say defines the risk.  The question becomes is how close to reality is that theoretical number?

To use "5" - as Consumer Reports does - is to say definitively that 5 is "safe."  "5," however, is just a threshold established by the EPA and New Jersey based on a theoretical calculation of a cancers potency (the Slope Factor).  That calculation, along with our technological ability to remove arsenic down to that level, is what sets the level which, for New Jersey, becomes known as "most protective."

If arsenic is a carcinogen, then less is better.  Period.  But with that in mind, exceeding a threshold based on a theoretical calculation does not make the product "troubling," "worrisome," "cause for concern," or "potentially harmful."

What does it make it then?  Good question.  Thanks for painting me into a corner.

All I can tell you is that exceeding 5 ppb does not make it "troubling," "worrisome," "cause for concern," or "potentially harmful."  Does that clear things up?  Now you see my problem with reports such as these.  They elude to something dangerous, when all that happened is that in some samples the threshold was exceeded.

That number detected - that concentration - would need to be significantly higher than 5 ppb before it got anywhere close to being "troubling," "worrisome," "cause for concern," or "potentially harmful"  So what would be considered significantly higher to warrant those concerns?  Good question, at least, in my opinion, rice that result in an 70 kg adult uptake of 56 μg of inorganic arsenic per day.  That would make me concerned (0.8 x 70 = 56 IRIS).  That would be at least six (6) servings of the highest concentration (9.4 μg/L) of inorganic arsenic Consumer Reports found in the rice.

But let's say the real hazard for arsenic is cancer, and that 10 ppb is not protective enough based on the Slope Factor's calculated.  In this case, we will need to look deeper into at how that Slope Factor was determined.  Is 5 ppb a good threshold?  Too restrictive?  Not protective enough?  We'll need to look at how they came up with it to make that call.


Next post: Arsenic in Rice:  Part 8 - How Low Can You Go?


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Arsenic in Rice: Part 6 - In the beginning there was a model

The issue I have with Consumer Reports looking into the amount of arsenic in rice is not that they report it, but that they and their experts do not honestly explain what the data means.  Yeah, they found arsenic, but they also sounded an alarm telling their readers that the concentration of arsenic they found was "troubling," "worrisome," "cause for concern," or "potentially harmful."

Consumer Reports, aided by public health experts they consulted with, drew a line in the sand stating that on this side it was "safe" and on the other side...well...:

We found significant levels of inorganic arsenic, which is a carcinogen, in almost every product category, along with organic arsenic, which is less toxic but still of concern. Moreover, the foods we checked are popular staples, eaten by adults and children alike. 

Once again, they drew a line in the sand using the New Jersey value for arsenic in drinking water as the threshold.

Using the 5-ppb standard in our study, we found that a single serving of some rices could give an average adult almost one and a half times the inorganic arsenic he or she would get from a whole day’s consumption of water, about 1 liter. 

What this implies is this:

By assuming that 5 ppb is safe, they imply that anything above that value is unsafe.  Make no mistake about that implication, that is exactly the message they want projected.  Arsenic is a carcinogen, therefore any amount of carcinogen cannot be anything but "troubling," "worrisome," "cause for concern," or "potentially harmful."

True statement that.  Can't argue against it, if that's true.  So I wont.

What I will argue against is accepting that 5 ppb is "safe" and anything above 5 ppb is unsafe.  Why argue this?  Because it assumes that 5 ppb is safe in the first place.  It assumes that 5 ppb is an acceptable threshold because New Jersey established it.  It assumes that 5 ppb actually represents a value that below which is protective of public health and above which presents risk.  Consumer Reports uses 5 ppb as a threshold for safe.  And by doing that, by drawing a line in the sand, they imply that rice with more than that amount is cause for concern.

What is troubling here is this.  5 ppb is not the value that represents safe, 0.003 ppb is.  If, and that is a huge if, the potency for arsenic is correct (the Slope Factor) then 0.003 ppb is the threshold not 5 ppb.  Therefore, exceeding 5 ppb does not fundamentally change the risk until that risk becomes significant.

Calling the arsenic concentrations they detected in rice "troubling," "worrisome," "cause for concern," or "potentially harmful," implies that the exceedance presented a significant risk.  Consumer Reports, however, does not address that, only stating that "we found that a single serving of some rices could give an average adult almost one and a half times the inorganic arsenic he or she would get from a whole day’s consumption of water, about 1 liter."

So I'll ask this question;  Does an adult consuming almost one and a half times the inorganic arsenic he or she would get from 1 liter of water increase their risk significantly enough to be "troubling," "worrisome," "cause for concern," or "potentially harmful."

Consumer Reports does not answer that question in their report.  They are very crafty on how it is written.  They do not answer it because they cannot.  This is the corner we paint ourselves into.  If there is zero threshold for carcinogens, and arsenic is a carcinogen, then any amount of arsenic presents a risk.  If we assume that 5 ppb is what we can get it down to, then we will set 5 ppb as the new "zero" and anything above 5 ppb will be "troubling," "worrisome," "cause for concern," or "potentially harmful."

Now I'll ask another question; Is 5 ppb a reasonable - or sound - number to use as the threshold?  After all, we know from reading the New Jersey justification that they chose 5 ppb, instead of 0.003 ppb, because it would not be technologically possible to treat the water to a level below 5 ppb.  In other words, New Jersey took the lowest possible concentration of arsenic that could be obtained.  They did this because the actual number they wanted is lower than that.  The assumption here is that 5 ppb is where we can get to, and going that low is necessary because the one in one million mandated risk concentration is calculated to be 0.003 ppb at that Slope Factor.

What if, however, that number - 0.003 ppb - is not a realistic - or sound - number?  What if the Slope Factor that was used to determine that risk of one in one million excess cancers is off?  What if the excess bladder and lung cancers actually seen in the United States is no where near the two in 1000 or one in 100 the scientists estimated in their modeling?  Would that change things?

Let's start here:

Arsenic in Drinking Water 2001 Update

When New Jersey set out to protect it citizens, it was faced with this little bit of the toxicological nightmare.  In order to protect public health we need to draw a line in the sand by establishing a threshold.  At one time the threshold for arsenic in drinking water was 50 μg/L

How did we get to 5 ppb?  Well it all starts here...

In 1988, EPA conducted a risk assessment for arsenic in drinking water and, in 1996 requested that the National Research Council (NRC), the operating arm of the National Academy of Sciences and the National Academy of Engineering, independently review the scientific database and evaluate the scientific validity of the risk assessment.  In response to that request, the NRC published Arsenic in Drinking Water in 1999.  following that report, EPA proposed an arsenic standard of 5 μg/L in the Federal Register.

That's from a document called Arsenic in Drinking Water 2001 Update produced by the National Research Council (NRC),  There are two things you should notice, one is that this is from the NRC and the second is the proposed arsenic standard of 5 μg/L.

To answer that question of how did we get to 5 ppb, it started here.  In fact everything involving the risk associated with arsenic in drinking water, the threshold Consumer Reports is using, started from this risk assessment.  That's what New Jersey used to justify their "most protective" limit of 5 μg/L.

[t]he New Jersey Drinking Water Quality Institute (Institute) reviewed the reports issued by the National Academy of Sciences (NAS) on the health effects of arsenic in drinking water in 1999, as well as an update of this report released in 2001 (Arsenic in Drinking Water: 2001 Update, NAS Press, 2001). Based on the current NAS analysis, the Institute determined that the drinking water concentration that results in a one-in-one-million excess lifetime risk of lung and bladder cancer for United States populations was an estimated 0.003 μg/l (or three nanograms per liter or three parts per trillion).

Hmmm.  So this is where the Slope Factor used to calculate the 0.003 ppb came from.  Interesting, I bet there will be something else of interest we can find other than a boring ol' history lesson.  Speaking of history, here is what we find out by reading the NAS report:

After review by EPA's Science Advisery Board (SAB) and a period of public comment, EPA issued a pending standard of 10 μg/L on January 22. 2001.  That pending standard was based on dose-response models and extrapolation from a cancer study of Taiwanese population exposed to high concentrations of arsenic in its drinking water.   

So, the EPA proposed standard was 5 μg/l and what we ended up with was 10 μg/L.  That threshold of 10 μg/L was based on a dose-response model, which means it was based on a non-cancer risk.  Interesting...they also extrapolated for cancer, but still did not find it necessary to drop it down to the proposed 5 μg/L.  Off course that was in January 2001, the New Jersey assessment was made in 2004.  So something happened to move the EPA away from a non-cancer dose response that supported 10 μg/L and to a cancer slope factor that would justify 5 μg/L?

Hold on to your hats, its going to get a bit bumpy from this point on.

Next post: Arsenic in Rice:  Part 7 - EPA and IRIS

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Arsenic in Rice: Part 5 - What Does "Most Protective" mean in New Jersey?

There is a reason for all these posts on one topic.  If you have read any of my other post, you will see that some 'splainen has to be done to support my conclusion.  I am pretty sure I know what my conclusion will be about Consumer Reports' research on inorganic arsenic found in rice.

It's not that they went looking for the arsenic that bothers me, it is how they describe what they found to their readers:

• "troubling" 
• "worrisome" 
• "cause for concern"
• "potentially harmful"

Those words mean something.  They mean exactly what they sound like.

So the question I am posing at this point in time, before I run through all the numbers, is; Is this terminology appropriate for the concentration of arsenic that Consumer Reports detected in the samples of rice they tested?

I like Consumer Reports.  I think they do good science.  However, as with their report on apple juice, they are not able to properly and/or adequately explain what the data they gathered actually means.  Like their report on arsenic in apple juice, this one regarding arsenic in rice uses expertise that support and conclude an incorrect conclusions on the risk.

I am starting to see a pattern here with these two reports and the experts they rely on.  These claims of  "troubling," "worrisome," "cause for concern," or "potentially harmful," are not supported by the data nor reality.  The experts Consumer Reports consults with must - or should - be aware of this.

It appears to me that the agenda of Consumer Reports is to protect public health by supporting a move towards lower and lower exposure levels.  In principle, this is a noble goal, but it is not necessary.  The EPA seems to be following this same philosophy, which is why I posted this quote from TCEQ's Dr. Honeycutt on my second post and also used it in my presentation at the AHMP conference two weeks ago.

So onward...

With a Slope Factor of 11.6  (mg/kg-day)-1, New Jersey estimates no more than one excess bladder/lung cancer out of a million over a 70 year lifespan for a concentration of arsenic in the drinking water of up to 0.003 μg/L

0.003 μg/L = 1 in 1,000,000 excess cancer risk over a lifetime based on drinking 2 liters/day.

The regulatory limit that New Jersey sets for arsenic in the drinking water is 5 μg/L.  New Jersey claims that this level is "most protective." (NJ)

So if 0.003 μg/L = 1 in 1,000,000 excess cancer risk over a lifetime, what is the excess cancer risk we will see at the "most protective" concentration of 5 μg/L.

Fun Time with Math!

....substitute 0.003 for 5, and we get a risk of 2 excess cancers per 1,000 (2.E-03)

5.0 μg/L = 2 in 1,000 excess cancer risk over a lifetime based on drinking 2 liters/day

You can calculate those numbers yourself, but that's what you get - and - they are consistent with the risk reported in supporting documents used by New Jersey (more on that in a later post):

Arsenic in Drinking Water 2001 Update

So if two excess cancers in 1000 is considered "most protective," would increasing that risk to three excess cancers in 1000 be considered  "troubling," "worrisome," "cause for concern," or "potentially harmful,"

If we are "most protective" at a concentration that theoretically will bring about 2 excess cancers in 1000, are we that more worse off at a concentration that increases that risk by one or two?

We need to stick some reality in here.  If 10 μg of arsenic consumed when drinking 2 liters of water brings forth 2 excess cancers in 1000, does New Jersey see that rate of cancer in their population?

Think about that for a moment.  Do we see that many bladder and lung cancers in the United States?  Remember, that's the estimated excess cancers from drinking 2 liters of water.  For those folks in New Jersey that drink two liters of water AND eat rice at 10 μg of arsenic, their rate of excess bladder/lung cancer doubles.  Do we see that many cases of bladder cancer?  I'll look at that in a few posts from now.

If Consumer Reports believes that the level of arsenic in rice should be at the "most protective" level set by New Jersey, then "troubling," "worrisome," "cause for concern," or "potentially harmful," is based on exceeding that level.  They are reporting that we are safe at a concentration that results 2 excess cancers per 1000 and harmful at anything above that.  Are we?

Did anyone at Consumer Reports ask this question; What is the actual rate of bladder and lung cancer in the United States?  If we know the concentration in rice is that high, are we seeing that much bladder and lung cancer in our population?


Next post: Arsenic in Rice:  Part 6 -  In the beginning there was a model

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Arsenic in Rice: Part 4 - Slope Factor...one more time!

I have written about the good ol' Slope Factor a number of times.  It is how we look at the risk from exposure to chemicals we view as carcinogens.  Carcinogens are where we have painted ourselves in the corner by claiming:

In contrast, the Federal SDWA sets an MCL goal of “zero” for carcinogens. (NJ)

You cannot have zero, so why even bring it up?  All it does is sets the stage for lower and lower exposure limits because zero becomes the goal.

If the cornerstone of the science of toxicology is accepting the premise that there is a "range of exposures from zero to some finite value can be tolerated by the organism with essentially no chance of expression of the toxic effect," then zero is just as relevant to protecting public health as some other number.  The quest is to find that number and set that as the threshold.

New Jersey has set the threshold at 5 ppb which it claims is "the most protective level within the constraints of medical, scientific and technological feasibility" for protecting public health from and "excess lifetime risk of lung and bladder cancer"

From my last post, we learned that 5 ppb is a threshold that was derived because of technological feasibility. In other words, ain't no way to treat water for arsenic to get it below that concentration.

The real number they wanted to see was 0.003 ppb which would give them an excess risk of one in one million excess cancers in a 70 year lifetime.

Now that we know those two values, 0.003 and 0.000001 (one in one million) we can calculate the slope factor they used in their calculation.

To do this we will use the method developed by California's EPA (CalEPA) for determining the "no significant risk level" (NSRL) for Proposition 65 "Known to the State of California to Cause Cancer" notifications.

Source

California uses a lifetime cancer risk at or below one in one hundred thousand (10-5 or 0.00001).  New Jersey sets the risk at or below one in one million (10-6 or 0.000001).  New Jersey law in this case aims to be more protective since zero is a non-attainable number.

What we need to do now is find the Cancer Slope, which CalEPA calls the qhuman.  The qhuman is a value described in terms of  (mg/kg-day)-1.

To get this value, we will need to convert our 0.003 ppb (which is in μg/L) to the amount in milligrams (mg).

So...if there are 1000 μg in a mg, the μg is 1000 times smaller than a mg.  Which makes 0.003 μg equivalent to 0.000003 mg.

Here is where it gets a bit confusing.  That number that New Jersey came up with, that's for a safe level of arsenic in drinking water for a life time excess cancer risk of one in one million.  A lifetime is 70 years and the amount of drinking water we consume is calculated on 2 liters a day.  So, the total amount of arsenic that would be consumed over a lifetime is 0.006 μg.

In other words, if a 70 kg person drank two liters of water a day, they would consume a total of 0.006 μg of arsenic from that water.  At that total amount, the drinking water would pose no more than one additional bladder or lung cancer in one million folks drinking the same water.

The key then is to keep the total arsenic from drinking water to at or below 0.006 μg or 0.000006 mg.

That total concentration is based on the potency of the carcinogen we are looking at.  That potency is called the slope factor and is a "theoretical estimate for humans" which CalEPA calls the qhuman which is in (mg/kg-day)-1.

Math time!

Using the CalEPA formula, I calculated the qhuman (Slope Factor) that was used by New Jersey to come up with the 0.003 μg/L for drinking water to give a lifetime cancer risk of one in one million excess bladder/lung cancers.

By my calculation, the qhuman (Slope Factor) = 11.6  (mg/kg-day)-1

That Slope Factor is consistent with the one the one the EPA uses for their male bladder cancer lifetime incidence estimate:

Table 5-3 Male Bladder Cancer Lifetime Incidence Estimate.xls

So now that we have the Slope Factor, we can look at the theoretical risk at different concentrations, such as 5 ppb and 10 ppb.

Next Post: Arsenic in Rice:  Part 5 - What Does "Most Protective" mean in New Jersey?

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