Apples, Arsenic, and Risk - Part 15: 19% more...67 years...carry the 2...

Consumer Reports states in their January 2012 report on arsenic in apple juice:

The resulting analysis of almost 3,000 study participants found that those reporting apple-juice consumption had on average 19 percent greater levels of total urinary arsenic than those subjects who did not.

If the average total urinary arsenic [NHANES] for 12-18 year old's is 8.55 ug/L, Apple juice drinkers would be - on average - 19% higher than that, or 10.17 ug/L.

The "long-term low-level arsenic exposure" was calculated as follows:

We estimated long-term low-level exposure by multiplying current estimated arsenic levels by the number of years residing in current home.

So an 18 year old would have a long-term low-level arsenic exposure of 18 x 8.55 = 153.9 ug/L-year.

And the 18 year old apple juice drinker would have a long-term low-level arsenic exposure of 18 x 10.17 = 183.1 ug/L-year.

So if the unstandardized regression coefficient - B - results are as reported, these are the scores we would predict between the two groups, average & apple juice drinkers, over an 18 year exposure period.

I ran their data in an Excel spread sheet so I could see what the difference would be between the two scores.  That's found in the last column at the bottom.  Notice how not one of those tests has a decrease or increase in the score over one (1).

The question I have is this: If the linear regression calculates an unstandardized regression coefficient called "B," and that we interpret an unstandardized regression coefficient as follows:

For every metric unit change in the independent variable, the dependent variable changes by X units.

The change in score these researchers report is so small as to be of little value.  Yet what was reported in this paper was used by Consumer Reports to make the claim that low-levels of arsenic below the drinking water MCL of 10 ug/L presents "a chronic problem" "related to poor scores in language, memory, and other brain functions."

Consumer Reports is using the conclusion of this paper to support their claim that:

Mounting scientific evidence suggests that chronic exposure to arsenic and lead even at levels below water standards can result in serious health problems.

Is this the" mounting scientific evidence" they are using to support their claim that low-level exposure is related to poor scores in language, memory, and other brain functions?

Did the researchers from Texas Tech and the University of North Texas find that "long-term low-level exposure to arsenic was significantly associated with poorer scores?"

Yes.  And that's the problem that needs to be addressed.

Numbers mean something.  Those "Bs" reported are valid in supporting their conclusion:

Our findings suggest an association between low-level arsenic exposure and neuropsychological functioning, as originally hypothesized. Of particular interest is the association between long-term low-level arsenic exposure and neuropsychological functioning across a broader range of domains than current exposure. Our findings offer the first direct evidence that low level arsenic exposure, extrapolated from current arsenic levels and self report of duration in residence is associated with poorer neuropsychological functioning among community-dwelling adults and elders in the U.S.

They found an association and the statistics - the p-value - supports it.  But what did they really find?

Or, more importantly, did they see results that would support lowering the level of arsenic deemed safe?  Are their results strong enough to stop us from drinking apple juice?  Should we, on the basses of a -0.001 change in a score require apple juice providers to reduce the concentration of arsenic from and average of 4 ug/L to 3 ug/L?

Why did four researchers produce this paper, and why did it it get published in a peer review journal?  Because there is nothing wrong with it in terms of it meeting the standards for publishing.

It's valid, it's honest, it's conclusion is correct.  Unfortunately it does not support the claim of "mounting scientific evidence suggests that chronic exposure to arsenic and lead even at levels below water standards can result in serious health problems."

It shows something that means nothing.  And that right there leads Consumer Reports, Dr. Oz, and good ol' Chuck Norris down the path of requiring a change where one is not needed.

As our investigation found, when scientists and doctors do look, the connections they’ve found underscore the need to protect public health by reducing Americans’ exposure to this potent toxin.

Why is this a big deal?  Let me quote the Texas Commission on Environmental Quality (TCEQ) once again:

[I]f erring on the side of conservatism significantly overestimates risk or hazard and is not  fully  justified, then harm to public health may result from diverting public, industry, and government attention and resources away from chemicals which may represent more of a public health risk at environmental levels. (TCEQ)

Next Post: Apples, Arsenic, and Risk - Part 16: The Great and Powerful Oz