Getting the News Straight on the CDC’s Exposure Report

The CDC’s Third National Report on Human Exposure to Environmental Chemicals came out last week. In a way, it became a blank screen upon which everyone projected all of their pronouncements (see here and here) related to chemical exposure. It was an example of a “persistent rage to conclude”, a wonderful phrase I’ve seen recently in an essay by Edward Tufte.

The Washington Post reports that levels of exposure to lead and metabolites from second-hand smoke have decreased, and quotes the CDC director as saying “[t]hese data help relieve worry and concern”. The Post however fails to cite the other conclusion about lead, that children of black and Mexican-American families, who are lower in the socio-economic spectrum, and live in urban housing constructed before 1950, are showing no decline in blood-lead levels.

Other newspapers choose to focus on the same message as the Post, which is “exposures are decreasing”. The LA Times chooses to focus on the other side of the message, that exposures are widespread with unknown health significance. The STATS web site at George Mason University, which “monitors the media to expose the abuse of science and statistics before people are misled and public policy is distorted,” (sort of an ACSH in academic garb) beats up the LA Times for distorting the story from CDC’s report, significantly without saying a word about distortions of the Washington Post kind. STATS then uses the CDC report to take a sideswipe at this study evaluating the possibility that phthalate exposures could result in alteration of sex ratios in humans; an object lesson of why we don’t put statisticians in charge of evaluating environmental risks to human health – alterations in sex ratios in response to environmental exposures is a matter warranting further examination.

The most sensible thing said in the press about the CDC’s report, quoted here from the LA Times article is:

"The report in general shows that people — kids and adults — are exposed to things that aren't intended to be in their body," said Dr. Jerome A. Paulson, an associate professor of pediatrics at the George Washington University School of Medicine and Health Sciences who specializes in children's environmental health. "In and of itself, that is a concern. Whether it's harmful or not we can't tell from this particular study."

This is why they are called “xenobiotics”.

With the different interests spinning the results to fit their needs (it’s nothing to worry about/it’s a real problem) and the press having a problem getting an accurate story out, there’s little wonder that this issue is very confusing to many people. There are some reasons for optimism – phasing out lead in gasoline, nonsmoking campaigns, and suspending use of aldrin and dieldrin as insecticides, seem to have resulted in exposure reductions. There are some reasons for concerns still – lead exposures remain elevated in some groups, exposures to phthalates are widespread and are not well understood. And, there are the exposures that CDC program is still getting around to, such as brominated fire retardants.