Monday, January 10, 2011

Chromium Water Contamination Could Do With More Science and Less Haze

by Duane Craig

Chromium Water Contamination
A widely held view is that there is no amount of drinking water contamination that is acceptable. The reality though is drinking water always has contained forms of contamination. No doubt more than one Native American took a long drink from a flowing stream not long after a buffalo relieved itself upstream in the very same water.

In earlier days too, some pioneers enjoying the unspoiled vistas of America raised water to their mouths that had just flowed over the rotting remains of a duck not far upstream. In both cases it could be those people experienced anything from a mild sickness to shorter lifespans. In those days, it was just the nature of living. Eventually you died and often no one really knew why.

I’ve read many reports about the Environmental Working Group’s (EWG) recent studies showing 31 of 35 U.S. cities had unacceptable levels of hexavalent chromium in their drinking water. This is the same stuff made famous by Erin Brockovich (not Julia Roberts) in the 1990s when she sued Pacific Gas and Electric for millions over a bubble of cancer cases in Hinckley, California thought to have been caused by the material.
Chromium has been involved with tanning, pulp, steel, metal plating, plastics, and dyes. The hexavalent variety is produced when chromite ore is roasted with calcium or sodium carbonate. In its 1998 “Toxicological Review of Hexavalent Chromium,” the EPA reiterated its 1996 findings that hexavalent chromium is a carcinogen in humans when inhaled and that it could not determine at the time if it was carcinogenic when ingested. Its latest report is under review and cannot be quoted from or cited at this time, but it only looks at the question of hexavalent chromium as a carcinogen when ingested.

While preparing this post I looked at the incidences of stomach cancer over a 20-year period (1988-2008) in San Bernardino County - the one where Hinckley is. The age-adjusted rate per 100,000 people for that period was 8.45. Across the state of California, the age-adjusted rate is 8.97 for the same period. When you look at the incidences of all cancers, San Bernardino County’s rate for the 20 years is 481.81, while the statewide rate is 494.57. San Bernardino has a lower cancer rate than 32 of the 47 counties in California. To be fair, there was an uptick in the rate of cancer cases from 1991 through 1994 when the age-adjusted rate exceeded 500, but it also jumped over 500 in 2001.

Even though there is some evidence mice and rats have gotten cancer from this material when ingested, you can find as many detractors who will cite valid studies showing how the biological differences of rodents cause the chromium to be more deadly to them. There is also knowledge cited by the EPA in its review referenced above that the human gastrointestinal tract converts hexavalent chromium to the more benign chromium trivalent and that less than five percent of the hexavalent variety is absorbed.

The EWG’s report has been called suspect by some and Anne Kolton, VP for communications for the American Chemistry Counci,l in a letter to the Washington Post commented that the EWG would not share its data and therefore it was “impossible to comment intelligently on a study without key information, such as methodology, specific findings, and peer-review process.”

No one wants to drink contaminants like hexavalent chromium but it seems Brockovich and now the EWG have added more haze to an already hazy issue.

Read some of the original and related Water Contamination stories here, here and here.


Anonymous said...

There's significant scientific evidence for links between ingested hexavalent chromium and cancer:

From California Environmental Protection Agency:

"Three studies have linked exposure to Cr VI in drinking water with statistically
significant increases in cancer of the GI tract (NTP, 2007; Zhang and Li, 1987; Borneff et
al., 1968). Zhang and Li (1987) was an ecological epidemiology study that revealed
statistically significant increases in the incidence of both stomach cancer and overall
cancer rates in rural villagers exposed to what appears to be high concentrations of Cr VI
in drinking water. The NTP (2007) study revealed a statistically significant and dose-
related increase in duodenum tumors in both male and female mice. Borneff et al. (1968)
was an animal study that revealed a statistically significant increase in the incidence of
tumors of the forestomach in female mice exposed to 500 ppm of potassium dichromate
in drinking water."

From the National Institute on Health:
NTP (2008). Technical Report on the Toxicology and Carcinogenesis Studies of Sodium
Dichromate Dihydrate in F344/N Rats and B6C3F1 Mice. NTP TR 546. National
Toxicology Program.

Zhang J, Li X (1986). Chromium contamination in the city of JinZhou. JinZhou Health
and Anti-Epidemic Station, JinZhou, China.

Beaumont JJ, Sedman RM, Reynolds SD, Sherman CD, Li LH, Howd RA, Sandy MS, Zeise L, Alexeeff GV. Cancer mortality in a Chinese population exposed to hexavalent chromium in drinking water. Epidemiology. 2008 Jan;19(1):12-23.

Duane Craig said...

@ Anonymous
Thanks for reading and commenting! I post the following not as support for any position but so readers can see a balance of information.

The studies you reference report on the Chinese study and the rat/mice studies. The Chinese study is well referenced with detailed explanations of the conditions that existed where the villagers were exposed to the material but they were exposed to 20ppm, a very significant amount. That study also didn't take into account the potential for airborne inhalation which could have been very high considering the amount of Cr VI pollution in the area. Both the EPA and California have pointed out the problems with the Chinese study and both generally don't think it advances the science. The Borneff study suffered from 8 weaknesses. The early rodent studies (MacKenzie and Lindberg) suffered from low sampling rates and low confidence in the databases. All of that is reported in the EPA's 1998 Toxicological Review of Hexavalent Chromium along with:

"Little data exist regarding health effects resulting from ingestion of hexavalent chromium. A single cross-sectional study was located that reported effects in humans resulting from ingestion of chromium-contaminated well water. Residents of a village in China were reported to have experienced oral ulcers, diarrhea, abdominal pain, indigestion, vomiting, leukocytosis, and presence of immature neutrophils. Other reports of toxic effects of Cr(VI) in humans are limited to case reports from accidental poisonings. With the exception of increased body burden of chromium, no significant adverse effects have been observed in animal studies following ingestion of chromium."

The EPA currently has a new review of the compound circulating that looks specifically at the ingestion of it. It is not the final version and so can't be cited or quoted. When released it will be interesting to see if the EPA will assign a cancer slope factor (CSF) and an age-dependent adjustment factor (ADAF) indicating a change in how it views the material since the 1998 review.

As for California, the Public Health Goal for
Hexavalent Chromium in Drinking Water is also a draft and so not reliable yet and subject to change.

There's no doubt in my mind Cr VI can't be good to drink but as is the case with alcohol and many other substances the quantity consumed could be key, and in the case of Cr VI that amount remains elusive.