A Canadian study, “Food Web–Specific Biomagnification of Persistent Organic Pollutants,” published in Science Magazine, identifies a new class of chemicals that pose a potential threat to human health. This conclusion results from a more fundamental insight: the traditional method of looking at bioaccumulation did so by studying marine life. However, air-breathing creatures discharge toxins differently than sea creatures, so some toxins that are not present in fish are in land animals, and they also become more concentrated as one moves up the food chain. The researchers expect most to be benign, but given the large number of substances (roughly 10,000) even if only a small percentage turns out to be toxic, it would still be a significant number.
From the abstract:
Substances that accumulate to hazardous levels in living organisms pose environmental and human-health risks, which governments seek to reduce or eliminate. Regulatory authorities identify bioaccumulative substances as hydrophobic, fat-soluble chemicals having high octanol-water partition coefficients (KOW)(100,000). Here we show that poorly metabolizable, moderately hydrophobic substances with a KOW between 100 and 100,000, which do not biomagnify (that is, increase in chemical concentration in organisms with increasing trophic level) in aquatic food webs, can biomagnify to a high degree in food webs containing air-breathing animals (including humans) because of their high octanol-air partition coefficient (KOA) and corresponding low rate of respiratory elimination to air. These low KOW–high KOA chemicals, representing a third of organic chemicals in commercial use, constitute an unidentified class of potentially bioaccumulative substances that require regulatory assessment to prevent possible ecosystem and human-health consequences.
This is potentially a big deal, for it involves thousands of chemicals, including fragrances, yet so far, it’s gotten little coverage in the US press (by contrast, it was easy to find on the BBC website). There is an AP story, but few outlets, save Forbes, seem to be picking it up. The only other most prominent news site in the Americas to carry a report so far is Bloomberg, but it was buried in the Canada section of the website:
Pesticides and fragrances are accumulating in people and Arctic land animals, part of a class of thousands of chemicals that need to be assessed for the potential to collect in the food chain, a study said.
Risk assessments currently look for chemical accumulations in fish. That misses substances that people and land animals retain and fish remove by breathing in water, according to a study by researchers at Simon Fraser University in Burnaby, British Columbia.
About one-third of the 12,000 organic chemicals in production fall into this category, constituting a previously unidentified class of potentially bio-accumulative substances, according to the journal Science, where the paper will be published tomorrow. New regulatory assessments are needed to prevent harm to the ecosystem and humans, the study said.
“As a society, we would be stupid not to feel the urgency of this paper’s call,” Sonya Lunder, a senior analyst at Environmental Working Group, a Washington-based watchdog, said in a telephone interview from Oakland, California. “This underscores the importance of making good decisions on the chemicals we are using in commercial products.”
Substances the study found concentrating in terrestrial organisms include the pesticides lindane, dicofal, endosulfan and trifluralin; musk xylene, a synthetic fragrance used in soaps and perfumes; and the intermediate chemicals tetradifon and tetrachlorobenzene.
Makers and handlers of trifluralin, a broadleaf herbicide used to control weeds in grass, cotton and soybeans, include Tyson Foods Inc., ConAgra Foods Inc. and The Andersons Inc., according to the Environmental Protection Agency’s 2004 Toxic Release Inventory. Tyson was unable to comment immediately. The other companies didn’t return calls for comment.
International Flavors & Fragrances Inc. made or imported at least 10,000 pounds of xylene musk in 1998, according to a U.S. Environmental Protection Agency database. Company spokeswoman Melissa Sachs said International Flavors has never produced the chemical.
Researchers found high concentrations of these chemicals in land animals, including wolves, seals and polar bears, and native Inuit people, and no accumulation was found in Arctic fish. Chemicals that don’t vaporize easily and dissolve readily in water have been overlooked because they don’t build up in fish and were assumed to be safe, the study said.
Toxins that can’t be excreted easily become concentrated in body fat as they move up the food chain, a process called biomagnification. Such was the case with DDT, a pesticide that contributed to a sharp drop in the population of bald eagles before it was banned.
Governments around the world are evaluating all commercial chemicals to identify substances that concentrate in food chains to levels that harm people and the environment, according to the paper.
More than 120 nations have agreed to eliminate PCBs, dioxins, furans and nine pesticides under the Stockholm Convention on Persistent Organic Pollutants, which took effect in 2004.
Fewer than 10 percent of chemicals in use are fully screened for human health effects, Lunder of the Environmental Working Group said. The study should help focus regulators’ attention on the chemicals most likely to cause harm, she said. Many chemicals, such as brominated flame retardants, were discovered to be accumulating in people by accident, she said.
“People in the U.S. still have chemicals in their bodies that were banned from commerce three decades ago,” Lunder said. “We’ve made some really big mistakes, and anything we can do to prevent learning that lesson with our own bodies and our own health is a really important tool.”
Below is the Associated Press story as reported on Forbes:
Tests that determine whether toxic chemicals accumulate in food may be missing some hazardous materials and need to be updated, a Canadian researcher said Thursday.
It has long been known that toxins can accumulate in the food chain, rising to higher concentrations as larger animals eat smaller ones.
But current tests for this accumulation focus on foods of aquatic origin, Frank A. P. C. Gobas, an environmental chemist and toxicologist at Simon Fraser University in British Columbia said in a telephone interview.
Researchers have found there are chemicals that do not accumulate in fish, but which do so in air-breathing animals, such as mammals, Gobas reports in a paper in Friday’s issue of the journal Science.
Bioaccumulation testing is done in the same way in most countries, Gobas said: “We’re all basically making roughly the same mistake.”
He said testing must be updated to cover chemicals that do not accumulate in marine life but may do so in air-breathing animals because of their slow rate of elimination during respiration.
Gobas said he has been studying the food chain of animals in the Canadian arctic where caribou eat lichen and wolves eat caribou. He said he found increasing accumulations of potentially toxic chemicals moving up that food chain, though the same chemicals did not accumulate in marine life. Further study found the same in other animals.
Was he surprised?
“Well, you’re always surprised, of course, but in hindsight I should not have been. It made us think about the process in a different way,” he said.