A Spread Of A Different Kind -- Butter Can Be Used To Measure Worldwide Air Pollution

Jones, a professor at Lancaster University in Lancaster, England, and his colleagues say that a pat of butter could be an effective monitor for atmospheric pollutants. Their conclusions are reported in the current (March 15) issue of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society. Traditional pollution analysis uses specialized air sampling devices that are larger, more expensive and more complicated than butter, according to the researchers.

The researchers see butter primarily as a way to estimate and monitor regional pollution levels. Butter samples then could be collected from different areas to estimate the international distribution of the pollutants, Jones said. Elevated regional pollutant concentrations could help investigators better determine the source of the emissions, he noted. The current findings with butter mirror known worldwide patterns of estimated persistent organic pollutant emissions, according to Jones.

Pollutants carried aloft by the wind eventually fall to Earth, often on pastures where cows graze. Persistent organic pollutants - which include PCBs (polychlorinated biphenyls), dioxins and some pesticides - then accumulate in the cows' milk fat, which makes up approximately 80 percent of butter, according to Jones. Margarine, which has less milk fat, is not as useful, he added.

Although airborne emissions can travel great distances, butter is "an important reflection of contamination levels in a local environment and gives an indication of potential exposure to contaminants," said Ruth Alcock, a researcher at Lancaster University who worked on the study.

Butter has been used previously to measure human dietary exposure to chemicals, she noted, but never before to monitor air pollutant levels. Consumption of the trace amounts of pollutants found in butter has shown no effect on human health, Jones said.

The study, a collaboration between Greenpeace Research Laboratories (who collected the samples) and the University of Lancaster (who conducted the measurements), evaluated butter samples from 23 countries. The researchers found that European and North American butter had the highest PCB levels. Lower contaminant levels were found in samples from the Southern Hemisphere, including Australian and New Zealand butters. PCB levels ranged from 110 to 3,330 picograms per gram of butter. A picogram is a trillionth of a gram, far smaller than the microgram levels that might cause a person harm, Jones noted.

Persistent organic pollutants, or POPs, are chemical substances that linger in the environment, bioaccumulate through the food chain, and pose a risk to human health and the environment, according to the United Nations Environment Programme, an international organization created to control the pollutants. The U.N. group calls for the reduction and eventual elimination of POP emissions.

In December, the U.N. officials announced that 122 countries, including the U.S., have negotiated a treaty to eliminate 12 specific persistent organic pollutants. Eight pesticides (aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex and toxaphene) are on the list, in addition to PCBs, dioxins, furans and hexachlorobenzene - an industrial chemical used to make synthetic rubber, ammunition and fireworks.

"With suitable controls, safeguards and further research," the researchers conclude, "we think that butter could be used to monitor the regional and global distribution of [POPs] and the effectiveness of international measures to reduce their emissions to the atmosphere."

Kevin C. Jones, Ph.D., is a professor in the department of environmental science at Lancaster University in Lancaster, UK.

Ruth Alcock, Ph.D., is a research fellow in the department of environmental science at Lancaster University in Lancaster, UK.