Studying the long-term effects of organic pollutants

It's no secret that what you put directly into your body can affect your heart health. Now there's growing evidence that remnants of some chemicals remaining in the environment and in the food supply may also contribute to heart disease risk. The list includes certain pesticides and industrial chemicals that have long been banned—but have not disappeared.

It's by no means clear that the pollutants themselves directly affect people's hearts—and even if they do, their impact likely pales in comparison to established risk factors such as smoking and obesity. Still, examining the effects of environmental toxins on the heart may help shed light on the possible causes of some disease.

One broad category of chemical contaminants is known as persistent organic pollutants, or POPs. These include older pesticides known as organochlorines (such as the infamous DDT) and polychlorinated biphenols (PCBs)—chemicals once used in appliances, fluorescent lighting, insecticides and more. Dioxins are another notorious group of POPs; they're formed as a byproduct of certain industrial processes or natural events, such as forest fires.

Organochlorine pesticides are now banned or restricted in the United States, as research has linked them to cancer and other potential health risks. PCBs were banned in the 1970s. Dioxins are still released into the air, water and soil—but at lower levels than a few decades ago.

True to their name, however, POPs remain in the environment for years. In particular, they build up in the fat and livers of animals and humans. Animal fat in the diet is the main route of potential exposure to POPs. And human body fat gives the chemicals a reservoir where they may remain.

The possible health effects

It's long been known that exposure to high levels of some POPs can have a detrimental impact on health, including an elevated risk of cancer. Research has also linked moderate POP exposure to heart-related problems. Based on lab studies in animals and human cells, POPs seem capable of disrupting normal hormone function and metabolism, which could have a host of implications.

Of course, what's seen in lab animals or human cells may not actually occur within the body. But a number of studies have now reported correlations between POP levels in a person's blood or urine and risk factors for heart disease, such as obesity, high blood pressure and diabetes.

In one recent study, for example, researchers measured blood levels of several POPs in about 2,000 older adults in Finland. Just over 15 percent had type 2 diabetes, the common form of diabetes related to older age and obesity. The risk of having diabetes was greater for people with the highest levels of organochlorine pesticides in their blood. Those with levels in the top 10 percent were about twice as likely to have diabetes as their counterparts in the bottom 10 percent.

The link, however, appeared to be limited to people who were overweight or obese—suggesting that POPs and body fat might act together to boost the risk of type 2 diabetes.

A more direct heart risk?

Of course, studies like this don't answer the question of whether POPs themselves are responsible for the higher rates of health problems. It's still not possible to state that there's a cause-and-effect relationship between POPs and higher rates of heart disease risk factors, nor has research established a solid link between POP exposure and heart disease itself.

But one recent study became the first to connect the chemicals to atherosclerosis. The study included 1,016 70-year-old Swedish adults who had their blood levels of different POPs measured and underwent ultrasound scans of the neck to check for plaques in the carotid arteries.

People with higher blood levels of certain PCBs tended to have more carotid artery plaques. The link remained when researchers accounted for weight, blood pressure, cholesterol levels and smoking habits. The study authors concluded that their findings simply "suggest" an effect of POPs on the risk of myocardial infarction. They cautioned that the link should be investigated in prospective studies.

Until additional studies are completed, however, preventing heart disease is, as always, a matter of overall lifestyle and working with your doctor to treat any existing risk factors you may have.

Publication Review By: Gary Gerstenblith, M.D., and Simeon Margolis, M.D., Ph.D.

Published: 03 Jul 2013

Last Modified: 03 Jul 2013