No one would choose to eat polychlorinated biphenyls, or PCBs — yet we unwittingly do. And a new study finds that the cost of their pervasive contamination of our food supply can be high blood pressure, a major risk factor for heart disease.

PCBs comprise a family of 209 related, colorless and oily compounds. Discovered more than a century ago, they quickly won widespread adoption as the electrical insulator of choice throughout the electric power industry. Being chemically stable and heat resistant, PCBs also found use in other applications: as lubricants, as additives to make plastics more pliable, in adhesives, even as a component of some inks.

Over the years, the toxicity of PCBs has slowly emerged. Some have been designated not only as probable carcinogens, but also as agents that diminish immunity and pollutants that lower birth weight and IQ. Now, researchers with the Anniston, Ala., Environmental Health Research Consortium report that these toxic pollutants also appear to impair vascular health.

A Monsanto plant in Anniston manufactured PCBs from 1929 to 1971. To probe for any lurking human impacts of widespread contamination in communities around the plant, the federal government funded a group of universities and community groups to study blood and other health indicators. For the new investigation, they focused on about 750 randomly selected men and women in the community nearest to the former PCB-production facility.

David Carpenter of the University of Albany, in Rensselaer, N.Y., and his colleagues discovered a dose-dependent climb in risk of both systolic and diastolic hypertension with rising blood concentrations of PCBs. “We’re excited by this relationship,” Carpenter says. “It’s very novel.”

His team reported the finding at the recent Dioxin 2009 conference in Beijing (the August meeting’s formal name is the 29th International Symposium on Halogenated Persistent Organic Pollutants).

The Anniston residents had been divided into three groups on the basis of blood-PCB concentrations. Those with less than 1.24 parts per billion were designated the reference group. The middle third hosted contaminant levels between 1.25 and 3.64 ppb. Group three: everyone higher than that.

After controlling for age, obesity, cholesterol and related blood lipids, gender, race, smoking and sedentary lifestyle — all risk factors for hypertension — PCBs linked strongly with blood pressure. The chance of having unhealthy systolic blood pressure — that maximum pressure, which occurs as the heart muscle contracts — was tripled in the middle PCB-contamination group and almost quadrupled in the highest PCB group. Compared to the reference group, risk of diastolic hypertension — a too-high minimum value in arteries while the heart is at rest — was more than quadrupled in the people who had mid-range PCB values, and almost quintupled in the most exposed group.

In all fairness, hypertension risks were measured in that slightly more than half of the recruits who were not taking medicine to control blood pressure.

So how typical were PCB levels in the Anniston recruits? In the general population, blood concentrations typically hover around 1 ppb, Carpenter says. In Anniston, the average is closer to 8, and some people tip the charts at values in excess of 300 ppb. But as the middle group demonstrated, concentrations didn’t have to be enormous to substantially elevate high-blood-pressure risk.

In fact, Carpenter’s group found, the only high-blood-pressure risk factor stronger than PCBs in this population was age. Not smoking. Not lipids. Not obesity.

A preliminary analysis of trends in people without hypertension indicates that even among them, relatively high blood levels of PCBs raised their blood pressure above background, Carpenter says. And while theirs is not yet in the clinically worrisome range, it could become so as these people age and/or gain weight.

For those of us fortunate enough not to live downwind or downstream of a former production facility, waste site or tainted building, there are ways to significantly minimize our exposure to PCBs. Being lipophilic, these pollutants settle into fats and oil. So fatty fish and marine mammals can provide rich reservoirs of the PCBs migrating around the environment. Which provides yet another good reason to keep whale meat firmly off of our menus. And cooks should grill — not fry — fatty fish so that any PCB-tainted fat can drip off.

Of course that doesn’t save us from livestock that have grazed on contaminated lands or eaten tainted fodder. That feed and grass can transfer PCBs into the fat of meat and milk.

Although the Environmental Protection Agency banned U.S. production and most uses of PCBs in 1979, these chemicals persist. Indeed, it’s their once-prized resistance to breakdown that allows PCBs to continue moving through the food chain even now, three decades after their ban.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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