Responding to the Freedom Industries chemical spill
Ken Ward has an excellent account in today’s Charleston Gazette of where the 1 ppm “screening standard” came from (hint: it’s not pretty) as well as examples of a much more scientific that should have been used. Here at Our Water WV, we have provided a lot of the same information, but Ken’s story puts everything in one story. As Ken quotes scientist Richard Denison:
“Now let me be clear,” Denison wrote. “I am not saying that the level of 1 ppm is unsafe. I am saying that we have no way of knowing whether it is safe. The data needed to make that assessment simply do not exist for this chemical.”
This is exactly what West Virginians should have been told about crude MCHM in their water from the beginning, because it is the truth.
Mr. Ward presents a much more scientifically rigorous alternative to the shaky 1 ppm “standard.”
In a post for her group’s blog, Natural Resources Defense Council senior scientist Jennifer Sass argued that the agency could have done the math differently, and come up with a more protective screening level.
Sass explained that the Eastman study used four chemical doses: No chemical (control), 25, 100, and 400 milligrams per kilogram body weight per day fed to each rat. Eastman’s authors said the mid-dose of 100 milligrams per kilogram had no effect, and therefore should be used to calculate a “safe” level for people.
“But that’s not what the data shows,” Sass wrote. Male rats had body weight decreases at all dose levels, including the low dose of 25 and the mid dose of 100, she wrote.
“The effect showed a dose-response trend, increasing with increasing dose, but the trend was not statistically significant,” Sass wrote. In female rats, the low- and mid-dose groups weighed ‘slightly more than controls’ but no specific measurements were reported and we are to trust the study authors that it was not statistically significant.”
Sass wrote, “It is hard to get statistical significance in studies like this where so few rats are tested at each dose, given the natural variation between individual animals.
“In statistical-ese, we say that the study is underpowered — its ability to detect an effect is very poor because the sample size is so small,” Sass wrote. “So, when such a study actually finds an effect, like this body weight decrease, despite its lack of power, it suggests a treatment-related effect.
“The chemical company may ‘overlook’ the effect at low doses, but government scientists charged with protecting the public’s safety shouldn’t be so dismissive of the toxic effects seen at the mid- and low-dose.”
Sass said if the CDC had used the low-dose figures from the Eastman study, the agency would have come up with a screening level far lower – 0.025 parts per million, or about 40 times more protective than the 1 ppm level.