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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