How PG&E's Scientists-For-Hire Reversed Findings of Cancer Study
Chrome-Plated Fraud: Chromium Pollution and Scientific Integrity
In 1959 the JinZhou Alloy Plant, located in a rural area in Liao-Ning province in northeastern China, began processing chromium ore. Its poor waste disposal practices quickly led to massive chromium-6 pollution. The plant not only released chromium-laced wastewater into a neighboring dry riverbed that cut through nearby villages, it also dumped thousands of tons of solid waste onto bare ground around the plant site. Rainwater percolating through the waste piles leached chromium-6 into the groundwater. 
When investigators from the JinZhou Health and Anti-Epidemic Station began sampling well water from nearby villages in early 1965, they discovered that almost a third of the wells in the two villages closest to the plant were contaminated with chromium-6. By the end of the year, the incidence of contamination had risen dramatically in these two villages, and sampling in three more distant villages revealed polluted drinking water and irrigation wells as well. By the 1970s, the contamination plume had spread to more distant villages.  The contamination wasn't contained until the early 1980s, when a concrete barrier was installed around the plant. 
Health surveys conducted from 1965 through 1974 found that residents in all five contaminated villages suffered from a variety of ailments associated with chromium-6 exposure: mouth ulcers, diarrhea, abdominal pain and vomiting. JianDong Zhang and XiLin Li, scientists assigned to the health station, published a series of articles in Chinese journals documenting the health problems.  Their work culminated in the 1987 paper in the Journal of Chinese Preventive Medicine that linked chromium-6 exposure to the higher rates of cancer found in the contaminated area.  This study has never been published in English, but the 1997 JOEM article summarized the earlier study's conclusion as "a significant excess of overall cancer mortality in five Cr+6 contaminated villages combined."  The JOEM article, published under the names of Zhang and ShuKun Li, comes to quite different conclusions. Its abstract reads:
This report is a clarification and further analysis of our previously published mortality study regarding groundwater contamination with hexavalent chromium (Cr+6) in the JinZhou area of China between 1965 and 1978. In our previous report, we stated that a significant excess of overall cancer mortality was observed (P = 0.04) in five Cr+6-contaminated villages combined. Further analysis revealed no clear statistical increase in cancer mortality in the three villages adjacent to the source of the contamination (P = 0.25), where 57% of the wells exceeded the European Community safe drinking water standard of 0.05 ppm Cr+6. These results do not indicate an association of cancer mortality with exposure to Cr+6-contaminated groundwater, but might reflect the influence of lifestyle or environmental factors not related to Cr+6. Further follow-up of this cohort is recommended. 
The 1997 study acknowledges that the five villages taken together still had high cancer rates, but reverses the 1987's study's conclusion that chromium-6 was to blame. The JOEM paper states that the villages closer to the chromium-6 plume had lower rates of stomach and lung cancer than those farther away, and that the cancer rates in the three villages closest to the source were not significantly higher than the surrounding province. The article also suggests that the Agency for Toxic Substances and Disease Registry should revise its assessment of the 1987 study in light of the new "findings":
"The absence of a dose-response relationship between cancer and Cr+6 clarifies a translation and interpretation of our previous publication made by the Agency for Toxic Substances and Disease Registry. Although Cr+6 contamination cannot be ruled out completely as the reason for the high cancer death rates in these villages, these results do not support such a relationship."