{"id":2916,"date":"2014-01-13T14:26:41","date_gmt":"2014-01-13T19:26:41","guid":{"rendered":"http:\/\/blogs.edf.org\/health\/?p=2916"},"modified":"2024-02-12T11:01:32","modified_gmt":"2024-02-12T16:01:32","slug":"west-virginia-officials-trust-shaky-science-in-rush-to-restore-water-service-one-part-per-million-safe-threshold-has-questionable-basis","status":"publish","type":"post","link":"https:\/\/blogs.edf.org\/health\/2014\/01\/13\/west-virginia-officials-trust-shaky-science-in-rush-to-restore-water-service-one-part-per-million-safe-threshold-has-questionable-basis\/","title":{"rendered":"West Virginia officials trust shaky science in rush to restore water service: One-part-per-million \u201csafe\u201d threshold has questionable basis"},"content":{"rendered":"

Richard Denison, Ph.D.<\/em>,<\/em> is a Senior Scientist.<\/p>\n

[SEE NOTE ADDED 1\/15\/14 BELOW]<\/em><\/p>\n

In a press conference today outlining plans to restart the water system serving 300,000 people, West Virginia state officials and executives from the West Virginia American Water utility company stressed that levels of the toxic chemical that contaminated the supply after last week\u2019s spill had reached a \u201csafe\u201d level of one part per million (1 ppm), the threshold agreed upon by state and federal officials on Saturday.<\/p>\n

Unfortunately, the science behind this standard remains unclear. \u00a0Based on what we do<\/i> know, there are good reasons to believe that officials are overlooking significant health risks.\u00a0 <\/p>\n

We know, for example, that the manufacturer\u2019s Material Safety Data Sheet (MSDS) that officials say they are using as their primary source lacks any information about chronic health impacts. The major federal databases we consulted<\/a> suggest such data simply do not exist for this chemical.<\/p>\n

It also appears that officials made significant leaps in their calculation of a \u201csafe\u201d exposure level \u2013 including assumptions that deviate from generally accepted practices. \u00a0As a result, these estimates fail to adequately account for either acute or chronic health effects from ongoing exposure to water contaminated at the 1 ppm level.<\/p>\n

At a bare minimum, the public deserves to know a lot more about the calculations behind officials\u2019 insistence that a 1 ppm level in drinking water is safe.<\/p>\n

\"Take<\/a>
Take Action: Support Stronger Toxic Chemical Standards \u00bb<\/a><\/b><\/figcaption><\/figure>\n

Do the math<\/b><\/p>\n

So how was this level, which is now being declared safe, derived?\u00a0 The short answer is, it was done through a mix of standard practice, problematic deviations from standard practice, and utter hand-waving.<\/p>\n

I blogged earlier<\/a> about how few health data are available on this chemical (4-methylcyclohexane methanol, or MCHM<\/a>; its unique identifying \u201cCAS number\u201d is 34885-03-5).\u00a0 With respect to oral toxicity, there appears to be only a single study, conducted in 1990 by the chemical\u2019s producer, Eastman Chemical Company, but never made public.\u00a0 That study uses one of the crudest methods around for assessing how toxic a chemical is:\u00a0 Feed rats the chemical and determine the dose at which 50 percent of the rats die in a short period of time, typically 24 hours.\u00a0 This dose is called the median lethal dose, or LD50.<\/p>\n

Using that crude test, Eastman apparently found the LD50 for this chemical was 825 milligrams per kilogram of body weight (this value is reported in Eastman\u2019s Material Safety Data Sheet (MSDS)<\/a> for what it calls \u201ccrude MCHM\u201d).\u00a0 Note that a \u201cmilligram per kilogram\u201d is equivalent to a part per million, or ppm.<\/p>\n

Officials started with that value and then applied a series of \u201cuncertainty factors\u201d as follows:<\/p>\n

1. Because humans may be much more sensitive to the effects of a chemical exposure than rats, a 10-fold \u201cinterspecies extrapolation\u201d uncertainty factor was applied.\u00a0 That dropped the value to 82.5 ppm.<\/p>\n

2. Because humans differ in their sensitivity to a chemical exposure (e.g., infants or the elderly or people with an illness may suffer effects at a dose that would not affect healthy adults), another 10-fold \u201cintraspecies extrapolation\u201d uncertainty factor was applied.\u00a0 That dropped the value to 8.25 ppm.<\/p>\n

3. Finally, acknowledging that the study in question looked only at lethality, whereas this chemical might well have other health effects short of outright killing you, a third uncertainty factor was applied.\u00a0 Magically, this factor was set at 8.25-fold, in order to produce the nice round number of 1 ppm as the \u201csafe\u201d level.<\/p>\n

[NOTE ADDED 1\/15\/14:\u00a0 Please note that the description above is not<\/span> of my own calculations. It is based on press reports<\/a> citing state and federal officials\u2019 account of the calculations used.\u00a0As described, the above calculations suggest that an overall uncertainty factor of 825 was applied:\u00a0 10 x 10 x 8.25.\u00a0 No official description has been released of the methodology used to derive the 1 ppm level<\/span>.\u00a0 Since posting this, I have discussed the matter further with a toxicologist familiar with similar situations, who notes a disconnect in the calculations between starting with a dose in the exposed animal (expressed in milligrams per kilogram of body weight) and ending up with a concentration in drinking water (expressed in milligrams per liter, equivalent to parts per million).
\nThe toxicologist speculates that a somewhat higher uncertainty factor may have been applied but notes many additional variables that may or may not have been taken into account, such as whether exposure of an adult or child was used as the basis (children consume less water per day but more in proportion to their body weight than do adults), or whether or not an additional uncertainty factor was applied to account for extrapolation from acute to subchronic or chronic effects.
\nThe toxicologist supported our core concerns noted below, however:\u00a0 use of a median-effect dose rather than a lowest no-effect or lowest-effect level as the starting point for the calculations; inappropriate use of a lethality study as the basis for setting a safe level for nonlethal effects; and \u2013 if such a study is to be relied on \u2013 application of too small an uncertainty factor in extrapolating from lethal to nonlethal effects.
\n\u00a0\u00a0\u00a0 All of this complication and confusion argues all the more strongly for transparency<\/b>:
\n* The officials should immediately release their methodology for calculating the \u201csafe\u201d level, and
\n* Eastman should immediately release the acute oral toxicity study and any other data it has on its chemical.]<\/span><\/i><\/p>\n

While the use of uncertainty factors is standard practice in risk assessment (being necessary because we don\u2019t generally intentionally test chemicals on people!), two major deviations from such practice were done in this case, based on highly questionable assumptions.\u00a0 Moreover, these calculations utterly fail to account for chronic<\/span> health effects from longer-term exposure to water contaminated at the 1 ppm level.\u00a0 Read on for the details:<\/p>\n