Friday, October 5, 2012

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


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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