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

If you thought 13 posts on the cancer Slope Factor was fun and interesting.  You are going to love this discussion on urine.

What do you get when you ask a bunch of Mormons to pee in a cup for five days?

You get some really good data (see footnote) on the correlation between urine arsenic and the arsenic in the drinking water they consumed.

That's going to be important in a little bit.  You see, when you read the Consumer Reports articles on arsenic in apple juice and rice you start to see a conclusion being pushed.  I can speculate as to why, but I am trying to make a case based solely on the data.  Speculation is the absence of that.  Nevertheless, you have to wonder about an agenda in play here, especially when you look into the work their subject matter experts have produced.

Case in point...here is what is quoted in Consumer Reports for arsenic in rice:

“We already know that high concentrations of arsenic in drinking water result in the highest known toxic substance disease risks from any environmental exposure,” says Allan Smith, M.D., Ph.D., a professor of epidemiology at the University of California, Berkeley. “So we should not be arguing to wait for years until we have results of epidemiologic studies at lower arsenic intake, such as from rice consumption, to take action.” His studies of arsenic in public water in Chile and Argentina helped show that it causes lung and bladder cancer and other diseases.

That Smith guy Consumer Reports uses as a subject matter expert, well he is one of the players in producing the data the NAS/NRC and New Jersey used to come up with the 5 ppb.

Source

...and his work is used all over the place in the 2010 draft IRIS toxicological review of inorganic arsenic.

Source

Here is what Dr. A. H. Smith states in the Consumer Reports article:

“So we should not be arguing to wait for years until we have results of epidemiologic studies at lower arsenic intake, such as from rice consumption, to take action.” 

No?  Instead we should base it on your data which in the draft IRIS document on arsenic we are told:

• Weaknesses include that arsenic levels were not available at the individual source level, dose response information was not provided, and only limited individual smoking history information was available (i.e., participants were asked if they had smoked cigarettes over a 1-month period in 1990). [Page 49]
• Weaknesses include that place of residence was determined from the death certificates, which relates to residence at the time of death, and the reliance on death certificates (potential diagnostic bias). Smoking, although considered unlikely by Smith et al. (2006), is a potential confounder for this study.

Okay...okay, my goal here is not to critique Dr. Smith's work, it is instead to show how certain statements, such as "troubling," "worrisome," "cause for concern," or "potentially harmful" are not supported by what we know about the 5 ppb threshold Consumer Reports is using to declare rice to not be "troubling," "worrisome," "cause for concern," or "potentially harmful."

I do want to look at Dr. Smith's statement that we "take action now instead of waiting for and epidemiologic studies at lower arsenic intake."  Dr. Smith is an E.  I am not an Epidemiologist (though I am staying at a Fairfield Inn in Alamogordo which is right next to a Holiday Inn Express as I write this, so....).

With that in mind, I will need to use other peoples work to make the case that the evidence before us does not show a need to "take action now" which would lead to this action:

Consumers Union believes a standard for arsenic should be set for rice.

After 13 posts, I hope I have shown how the current proposed Slope Factor that leads to a "safe" threshold of 5 ppb - which is used by New Jersey for drinking water - does not mean there is harm, or unnecessary risk, when consuming rice at up to 10 μg arsenic per serving.

Okay, you may be saying, ...but what about the fact that rice eaters have higher amounts of arsenic in their urine?  Huh?  What about that???  Doesn't Consumer Reports state:

People who ate rice had arsenic levels that were 44 percent greater than those who had not, according to our analysis of federal health data. And certain ethnic groups were more highly affected, including Mexicans, other Hispanics, and a broad category that includes Asians. (CR)

So let's run with that, shall we...

According to their subject matter expert, Dr. A. H. Smith:

Urinary arsenic concentrations give a good biomarker of the absorbed dose of arsenic, since about 70% is excreted in the urine.  Excretion of arsenic in urine as a function of exposure to arsenic in drinking water. (AJE) 

Here is what Consumer Reports tells us:

Researchers at the Dartmouth Children’s Environmental Health and Disease Prevention Research Center in late 2011 published a small but informative study that indicated consuming slightly more than a half-cup of cooked rice per day resulted in a significant increase in urinary arsenic levels, comparable to the effects of drinking a liter of water containing the federal maximum of 10 ppb arsenic. The authors say their results suggest “many people in the U.S. may be exposed to potentially harmful levels of arsenic through rice consumption.”

I went to the Dartmouth Children’s Environmental Health and Disease Prevention Research Center's web page and looked up everything they had on arsenic.  I cannot find anything dated in 2011, but what I did look at does not state anything like "many people in the U.S. may be exposed to potentially harmful levels of arsenic through rice consumption."  Here is what their research and papers state:

• Despite these limitations, our findings suggest that rice is a potential source of arsenic exposure in U.S. children and highlight the need to better understand the health consequences of common levels of arsenic exposure early in life. (1)
• Our study suggests that rice consumption is a potential source of arsenic exposure in U.S. children. (2)
• There is some evidence that high levels of arsenic exposure during childhood are associated with neurobehavioral problems as well as cancer and lung disease later in life. However, further research is needed to understand the health effects of exposures like those observed in this study. (3)

I am not in any way shape or form implying that arsenic is not a health concern.  I am making an argument that the amount of arsenic reported to be found in rice sampled by Consumer Reports is not in any way shape or form "troubling," "worrisome," "cause for concern," or "potentially harmful," if it exceeds 5 μg per serving.

Continuing on...

Have I ever mentioned how glad I am to work for a University where I have access to their library...I looked up that Dartmouth report, where I read this:

Among the roughly one-quarter of Americans who report rice consumption, the average amount of rice consumed is approximately 1 cup of cooked rice per day

So here is what we know so far:

• Urinary arsenic concentrations give a good biomarker of the absorbed dose of arsenic, since about 70% is excreted in the urine. 
• Rice eaters had arsenic levels that were 44 percent greater than those that do not consume rice.
• The average amount of rice consumed is one cup.
• Consumer reports measured the amount of inorganic arsenic in one serving of rice and found the highest level to be 9.6 μg per 1/4 cup.

Looking closely at the urine...remember, science is fun...we can start to get an idea of how much inorganic arsenic is actually being consumed.  And, with that information we can ask the question do we see an increase in bladder cancer for those rice eaters compared to the general public as a whole?

The premise here is based on this:  If arsenic increases the risk of bladder cancer (which is what the Slope Factor is based on) then those who are exposed to more arsenic (rice eaters) would show more incidence of bladder cancer.

Let's see what the data shows....


Source: Calderon RL, Hudgens E, Le XC, et al. Excretion of arsenic in urine as a function of exposure to arsenic in drinking water. Environ Health Perspect 1999;107(8):663-667.

Next post: Arsenic in Rice: Part 15 - Urine From Rice Eaters


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