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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