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It's great on toast, but it harbors small concentrations of nasty organic chemicals. Could these traces be used to monitor global movements of persistent organic pollutants?

EPA

While gathering field data, some environmental scientists swat mosquitoes or dodge homicidal rebels. When Kevin Jones gathers data on persistent organic pollutants, he might pick up a loaf of bread.

That's because Jones's "field" is the grocery store, and his quarry is a domestic "sampling matrix" called butter. Instead of measuring persistent organic pollutants (POPs) by, say, sneaking a probe into a sleeping polar bear, Jones adheres to his life-extension program by measuring POPs in butter instead.

Sure, you're thinking, "Nice work if you can get it," but why bother?

The research responds to gathering concern about persistent organic pollutants -- nasty but useful chemicals that last decades in the environment. The popular POPs include pesticides like dieldrin and DDT and industrial chemicals like hexachlorobenzene. Other pestiferous POPs include the dioxins and furans, which are byproducts of burning.

Overstaying their welcome
POPs commonly linger for decades in the environment, or decompose into other toxic chemicals. POPs have been appearing in remote regions of the globe and, because they cause cancer and reproductive problems, can cause considerable consternation.

Resistance to breakdown helped make POPs popular in the first place: PCBs were a good, stable insulator for electrical transformers. POPs travel well: PCBs that moved north with the wind were deposited in the fat of polar bears in the Arctic -- a place that should be fairly pollution-free. (POPs accumulate in body fats, and particularly concentrate in animals atop the food chain, like those polar bears.)

The POPs are such a nuisance that, in December, 2000, 122 nations decided to phase out 12 major varieties. One United Nations official described the treaty as a "declaration of war against persistent organic pollutants."

But how common are POPs in a particular region? It's expensive to track a bunch of low-level, low-life chemicals with air monitoring equipment, but how else would you do it?

Widespread spread
You might remember how nicely POPs collect in fats, and focus on a common fat -- butter. When cows eat plants that have accumulated POPs from the atmosphere and soil, they conveniently excrete the chemicals into their milk, where it is pooled, processed and delivered in nice packages to Kevin Jones's field sites.

Once you correlate butter contamination levels to air levels, you have a cheap, comprehensive measure of POPs levels in a dairying region. That's the theory, at any rate, although the results are affected by the techniques used to feed cows in each dairy region.

With sample-collecting help from Greenpeace Research Laboratories, Jones, a professor of environmental science at Lancaster University in the United Kingdom, and colleagues used high-performance liquid chromatography to analyze butter from 23 nations. HPLC is a common lab technique for separating and identifying organic compounds.

POPs and the high-price spread
PCB levels were highest in Europe and North America, and lowest in New Zealand and Australia. In both cases, the butter-borne results were in line with concentrations measured with conventional filter technology.

The butter concentrations of PCBs generally measured in parts per trillion, low enough that, Jones says, they pose little threat to humans. (Still, eating butter and other fats is the main route for ingesting POPs, and less is better than more.)

However, some measurements of the pesticide DDT and its breakdown products were considerably higher. The one sample from India, where DDT is used to kill malarial mosquitoes, measured 0.25 milligrams per gram, or 250 milligrams per kilo of butter.

Polar bear image, courtesy USFWS/Dave Olson

That's a lot of DDT, especially in a country where ghee, clarified butter, is a standard cooking ingredient.

Which brings us full circle. We forgot to mention one last advantage of the better butter method. Those leftover samples are tastier on toast than gobs of polar-bear fat.

-- David Tenenbaum

Bibliography:
The Global Distribution of PCBs and Organochlorine Pesticides in Butter, O.I. Kalantzi et al, Environmental Science and Technology, 2001, 35: 1013-18.