No federal limit exists for arsenic in most foods, but the standard for drinking water is 10 parts per billion (ppb). Keep in mind: That level is twice the 5 ppb that the EPA originally proposed and that New Jersey actually established. 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. (CR)In their earlier report on arsenic and apple juice they write:
The Environmental Protection Agency periodically revises its assessment of the toxicity of various chemicals to offer guidance on drinking-water standards. Based on such a review, the agency changed the water standard for arsenic to 10 ppb, effective in 2006, from the 50-ppb limit it set in 1975. The EPA had proposed a 5-ppb limit in 2000, so the current limit is a compromise that came only after years of haggling over the costs of removing arsenic. Since 2006, New Jersey has had a 5-ppb threshold, advising residents that water with arsenic levels above that shouldn't be used for drinking or cooking. (CR)According to Consumer Reports, the New Jersey "5-ppb threshold" is the standard to which arsenic concentrations in the items we consume should be compared to. This assumes that we are all on board with the idea of a threshold concentration below which we would consider the foodstuff to be "safe."
Why 5 ppb? What does New Jersey know about the risk of arsenic in drinking water that the EPA does not know? The EPA has a enforceable limit, a threshold, they call the maximum contaminant level (MCL) and has set the concentration at 10 ppb.
As Consumer Reports reminds its readers to "Keep in mind: That level is twice the 5 ppb that the EPA originally proposed and that New Jersey actually established" one must assume that 5 ppb is therefore "safe" and 10 ppb is, well, err..."troubling", "worrisome," or "potentially harmful?"
Where did that number "5-ppb" come from? How did they end up with 5 and not 6, or 3, or 10? One of the cool things about the government is that before it makes a regulation it has to put it out there for public comment. The other cool thing is the internet and Google!
Here is what New Jersey says is their justification for a threshold of 5 ppb and not 10 ppb like the EPA uses for its MCL.
The NJSDWA differs from the Federal SDWA regarding the process for establishing MCLs. For carcinogens, the NJSDWA mandates a cancer risk level of one-in-one-million additional cancer cases over a lifetime of exposure. (NJ)What does the New Jersey say about arsenic as a carcinogen?
Arsenic is one of a relatively small number of chemicals that has been classified by the USEPA as a known human carcinogen, based on human epidemiological studies. Exposure to high concentrations of arsenic through drinking water has been linked to several types of cancer, including skin, lung, and bladder cancer. (NJ)So New Jersey sees arsenic as a carcinogen therefore they mandate "a cancer risk level of one-in-one-million additional cancer cases over a lifetime of exposure."
Which means that 5 ppb must be the maximum level of arsenic in a liter of water that will meet the threshold of "one-in-one-million additional cancer cases over a lifetime of exposure." That's correct isn't it? 5 ppb is the threshold for the mandated cancer risk level of "one-in-one-million additional cancer cases over a lifetime of exposure?"
Yeah, I'm beating to hell that dead horse but this is important and it gets to the heart of the matter when looking at concentrations above a threshold. If New Jersey law mandates a one in a million cancer risk, then 5 ppb must be the maximum concentration so that at or below we would see no more than "one-in-one-million additional cancer cases over a lifetime [70 years] of exposure."
That 5 ppb is what Consumer Reports uses as the threshold for rice. And when their analysis showed levels above that, they printed them in red and used terms such as "troubling", "worrisome," "cause for concern." or "potentially harmful."
If the arsenic threshold is set by New Jersey at the concentration that will bring a cancer risk level of one-in-one-million additional cancer cases over a lifetime of exposure, is 5ppb, then any concentration above 5 ppb will increase that risk to more than one. How much above one would we consider too much risk?
Now New Jersey had to do some toxicology and risk calculations to get to this number. And good ol' government transparency makes that information public knowledge. Since they were "mandated" to derive a cancer risk level of one-in-one-million additional cancer cases over a lifetime of exposure, they did the calculation and found:
Based on the current National Academy of Sciences (NAS) analysis, the New Jersey Drinking Water Quality Institute (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). (NJ)Wait...does that say 3 parts per TRILLION? Huh? The threshold New Jersey uses to say the water is "safe" - and the threshold that Consumer Reports uses to claim rice that exceeds that threshold to be "troubling", "worrisome," "cause for concern." or "potentially harmful" - is 1666 times higher than the concentration that "results in a one-in-one-million excess lifetime risk of lung and bladder cancer."
Lucy! You got some 'splainen to do!
According to New Jersey:
Therefore, in view of its concerns regarding reliable removal technology, the Department determined to promulgate the arsenic MCL at 5 μg/l [ppb]. 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. (NJ)So it is 5 ppb instead of 0.003 ppb because arsenic in water cannot currently be treated to a level below 5 ppb. Well then why is the EPA at 10, if 5 ppb is "most protective?" Well you see...
USEPA conducts a cost-benefit analysis that considers the implementation costs of an MCL for water systems and their customers, which in some cases results in adjusting the MCL to a different level than might be the case if such costs were not considered. Because the MCL-setting process under the NJSDWA does not include a costbenefit analysis, the State MCLs for certain contaminants, such as arsenic, are more stringent than the Federal MCLs. (NJ)Well now, isn't that nice, reality and costs come into play when trying to figure out a threshold. So if 0.003 ppb is what we really need to be protective, how much more lung and bladder cancer above one-in-one-million additional cancer cases over a lifetime of exposure are we expected to see?
And, based on those numbers of additional cancer, how many more would we see at 10 ppb? And then, in looking at those numbers, if we assume, as New Jersey does, that 5 ppb is the "most protective level within the constraints of medical, scientific and technological feasibility," how much less protective would 10 ppb of arsenic in the drinking water be. If 0.003 ppb spits out a number of one-in-one-million, 5 ppb and 10 ppb will spit out a number as well.
So, once we know the x-in-one-million number for 5 ppb, we can compare the y-in-one-million number for 10 ppb to see if that number, y - x, is so high that we would consider it to be "troubling", "worrisome," "cause for concern." or "potentially harmful."
Remember, the number we will get for 5 ppb is considered "most protective" so how much above that x-in-one-million number can be considered "troubling", "worrisome," "cause for concern." or "potentially harmful?"
Cool, we get to use the slope factor.
Next post: Arsenic in Rice: Part 4 - Slope Factor...one more time!
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