ATLANTA (Legal Newsline) - A study that found indications of a link between chemicals in the PFAS family and cancer was designed from the outset to establish the level of proof for civil lawsuits, not scientific certainty, one of the study’s authors said.
While there is mounting evidence that high exposures to two chemicals can cause kidney cancer, more research is needed to determine whether that link persists at low levels of exposure as well as whether PFAS causes other diseases, said Kyle Steenland, an epidemiologist at Emory University’s Rollins School of Public Health.
His sentiments echo critics of a rush to regulate and litigate over PFAS who say the scientific community hasn't reached an actual conclusion on their health effects.
As part of a class action settlement in 2005, DuPont funded the research into the health histories of some 69,000 residents known to have been exposed to PFOA and PFOS. The two chemicals were once used for the production of a variety of products including Teflon and firefighting foam but have largely been discontinued. Both belong to the larger family of chemicals known as PFAS, molecules which because of their high solubility and durability persist in the environment and human tissue for years.
The DuPont-funded Science Panel study was designed to find a “probable link” between exposure to PFOA or PFAS and some 50 chronic diseases. The term “probable link” doesn’t mean there is a scientifically established cause-and-effect relationship between a chemical and disease, but could meet the lower legal standard in jury trials, which is more likely than not.
“It’s a legal term,” Steenland said. “We were charged by the court to decide that. There were three of us and we had to vote.”
To reach the higher scientific standard of causality, Steenland said, researchers must perform more studies to identify disease patterns associated with exposure to the chemicals and to rule out confounding factors such as age, sex, income levels and education. All are known to have significant correlations with disease and so researchers try to stratify the data according to potential confounders and see if the connection to disease persists.
There was a “clear association” with kidney and testicular cancer and PFOA, which increased with the level of exposure, Steenland said, suggesting further research could solidify that link. But evidence of a larger association between the PFAS family of chemicals and cancer “remains sparse,” Steenland and Andrea Winquist of the Centers for Disease Control concluded in a recently published article funded by the CDC.
Studies now under way in Italy and Sweden might provide more evidence for or against a disease connection.
Lawyers have focused on PFAS because it can be detected in parts per trillion in drinking water and human tissue, making it an ideal subject for litigation.
“It’s the ultimate mass tort,” said Joseph Anotti, president of the Center for Truth in Science, which studies science in the courtroom. “Literally every human being in the U.S. could be a plaintiff.”
Trial lawyers are working closely with Democratic politicians to push for tighter regulations of the entire PFAS family, he said, in part because those regulations would then make it easier to sue under federal laws like the Clean Water Act that provide for private rights of action. The Center for Science in the Public Interest, for example, is registered as a lobbying organization and promotes regulations that align closely with the interests of trial lawyers.
“Regulation is typically enforced through litigation,” Anotti said. “So there’s a very close connection between regulatory enforcement and litigation.”
State attorneys general are also hiring private lawyers to pursue lawsuits over PFAS, under which those lawyers could earn substantial fees. All the PFAS lawsuits hinge upon the miniscule exposures detectible with new techniques, without scientific evidence to establish they are actually responsible for disease.
Steenland of Emory Public Health said the Science Panel benefited from the large number of subjects with varying levels of exposure to PFOA and PFOS. That allowed the panel to study the dose-response relationship, a key indicator that a substance causes disease. In many cases, researchers have only subjects with low levels of exposure, making it harder to strip out the effects of confounding factors and establish a firm relationship between a chemical and disease.
On the other hand, Steenland said, because the exposures in the study of people who lived near DuPont chemical plants were relatively high, he said researchers are unsure how important their findings are for low exposures. Beyond the connection to kidney cancer, he said, much more research is needed.
Steenland also said it is unknown how many of the effects they found with PFOS and PFOA can be extended to the entire PFAS family.
“I think they are probably related in what they do in the body,” he said, “but we don’t know enough about it to be sure.”