Persistent Organic Pollutants or POPs include many of the ugly toxins that have insidiously bioaccumulated across the world as the industrial-scale manufacture of synthetic chemicals escalated after World War II.

The 1960 and 70s were the years of bioaccumulated organochlorines - decades we can identify with Rachel Carson and her landmark book that challenged the US chemical industry, Silent Spring.

The 1980s and 90s were the years of the bioaccumulated polychlorinated biphenyls (PCBs) and dioxins - decades where we might remember the use of defoliants by the Untied States over the forests of Vietnam (2, 4-T; 2,4,5-D; Agent Orange) [the same chemicals were used by Queensland Premier, Joh Bjelkie-Petersen who proudly boasted that he’d used leftover Vietnam War Agent Orange as a defoliant to aerial spray thousands of square kilometres of the Brigalow Scrub of inland Queensland!].

The 1990s and the 2000s were the decades of the new synthetic kids on the POPs block - the polybrominated diphenyls (PBDEs) - benignly referred to as “flame retardant chemicals”.

Different commercial PBDE flame retardant formulations in use, include penta(5-)brominated diphenyl ethers in furniture foam; deca(10)-brominated diphenyl ethers in plastics for television cabinets, consumer electronics, draperies and upholstery; and octa(8)-brominated diphenyl ethers in plastics for personal computers, mobile phones and small appliances. Because they do not bind chemically with plastics, they leach continuously out of the final manufactured produced and they enter the atmosphere. 

Human data on health effects of PBDEs are limited; the U.S. Environmental Protection Agency (EPA) cites animal tests as evidence that PBDEs are powerful neuro-developmental toxins, disruptors of thyroid functions, and liver toxins. The specific toxic effects of brominated flame retardants are only beginning to be investigated, but public health officials are concerned because low concentrations in laboratory and companion animal are associated with various nervous system and reproductive effects, such as impaired learning and development; hyperthyroidism, and some cancers.

The main U.S. manufacturer first announced plans to discontinue their use as part of a voluntary agreement with the U.S. EPA; USA completely stopped the manufacture of penta-BDE and octa-BDEs in 2004. About 50,000 tonnes of PBDEs are produced annually world-wide. Scandinavian surveys show that this group of chemicals has increased dramatically as a residue in human breast milk.

Pathways by which PBDEs enter the natural environment and humans are only now beginning to be investigated. Living in a plastic-fantastic world (carpets, furnishings, plastic appliances, padding, and some forms of packaging); their volatility and ability to leach from plastics products as they age or when subjected to heat; their ability to adsorb onto organic matter, their persistence and the ability to biomagnify within the food chain has put these chemicals onto the eco-toxicology watch lists. It is therefore not surprising that PBDEs are found in the natural environment, bioaccumulating from the less complex lower organisms up the food web to more complex organisms. The European Union has banned two types of PBDEs — the penta-BDE and octa-BDE — and is currently considering a ban on the deca-BDE. They are classic POPs and yet they are still not included in the Stockholm Convention of Persistent Organic Pollutants.

The detection of the PBE 209 (2,2’,3,3’,4,4’,5,5’,6,6’- Deca-bromodiphenyl ether) in the tissue fat of Tasmanian devil samples will undoubtedly increase pressure on banning this deca-BDE; as this congener was not acknowledged as a potential bioaccumulation risk chemical.

Food Safety Issues

In August, 10 2004 a toxicology survey appeared in Environmental Science & Technology -a peer-reviewed journal of the American Chemical Society. The authors (professional toxicologists & chemists) reported that PBDEs were released into the environment both at their manufacturing sources and through everyday exposure and wear & tear to products containing these chemicals.

The chemists also measured PBDEs in 700 samples of farmed and wild salmon from around the world (all except Tasmania), including most major salmon-producing regions. The study, which is by far the largest of its kind, used the same samples from an earlier study that revealed significantly higher levels of organo-chlorine chemicals like PCBs and dioxins in farmed salmon than in wild salmonids. They also reported that with one exception all farm-raised fish samples had much higher levels of PBDEs than wild salmon. They also found that farmed salmon from Europe had higher levels than those from North America, and that both European and North American farm-raised salmon had higher levels than those raised in the southern hemisphere (southern South America - Chile).

The findings suggest that, in spite of marketing advantage of the heart-healthy omega-3 fatty acids found in all salmon, consumers should limit their intake of farmed salmon and wild Canadian Chinook salmon.  From the data in their earlier study on PCBs and dioxins, the researchers recommended humans eating only two meals of farmed salmon per month or less, based on U.S.
Environmental Protection Agency standards. But since no standards exist yet for PBDEs, a similar quantitative suggestion can’t be made presently.

From an organic chemistry perspective, the structures of PBDEs look very similar to the persistent PCBs and Dioxins. The background concentrations of PBDEs are rising continuously while residue levels of all the organochlorine chemicals (Organochlorines, PCBs, and Dioxins) are declining as international regulation on disposal & bans on production improve. 

Companion animals are the ‘canaries’ in the coal mine.

A mysterious epidemic of thyroid disease among pet cats in the United States is linked to exposure to dust from flame retardants in household carpeting, furniture, fabrics and also present in some commercial pet food; this is the opinion of veterinarians and eco-toxicologists.

In mid-2007 scientists at the U. S. Environmental Protection Agency and colleagues, Indiana University and the University of Georgia reported evidence linking the feline hyperthyroidism to exposure to polybrominated diphenyl ethers which the researchers found to be elevated in blood samples of hyperthyroid cats. Their findings were based on analysis of blood samples from 23 pet cats, 11 of which had the disease, termed feline hyperthyroidism. PBDE levels in the hyperthyroid cats were three times as high as those in younger, non-hyperthyroid cats.

Concerns about the possible health effects of PBDEs arose in the late 1990s, and studies have reported that PBDEs cause liver and nerve toxicity in animals. Hyperthyroidism is one of the most common and deadly diseases in older cats and indoor pets are thought to be most at-risk. Pet cats ingest large amounts of PBDE-laden house dust that the researchers believe comes from a range of consumer household products.

Eco-toxicologist, Janice Dye began by hypothesizing that prolonged contact with certain polyurethane foams and components of carpet padding, furniture and mattresses would pose the greatest hazard for developing hyperthyroidism. In addition, the researchers suspected that the foods in the diet might be another risk factor.

To see if a link existed, they analysed PBDE content in several cat food brands. They found that PBDE content of canned fish/seafood products, such as salmon and whitefish, was higher than dry or non-seafood canned items. Based on the analysis, they estimate that diets based on canned food could have PBDE levels 12 times as high as dry-food diets. The researchers indicate that pet cats might be receiving as much as 100 times greater dietary PBDE exposure than American adult humans.

With their meticulous grooming behavior, cats may ingest large amounts of dust that collect on their fur. Because PBDEs are potent endocrine-disrupting agents, these pet cats were at increased risk for developing thyroid effects.

The danger of contracting feline hyperthyroidism might be greater in America, where people have the highest reported PBDE levels worldwide, the study said. Also, by the late 1990s, North America accounted for almost half of the global demand for PBDEs from commercial materials like furniture or upholstery, the report added.

The epidemic of hyperthyroidism in cats began almost 30 years ago, at the same time when PBDEs were introduced into household materials as a fire-prevention measure. Although the disease was first discovered in the U.S., it has since been diagnosed in Canada, Australia, Japan and many parts of Europe. Hyperthyroid disorders have also increased in humans - former President George H. W. Bush (senior) and his wife, Barbara Bush have the disorder; even Millie, their Springer Spaniel, had contracted it.

Symptoms of the syndrome in pet cats include weight loss, an increase in appetite, hair loss and irritability. Cats and humans are the only mammals with high incidences of hyperthyroidism. The study concludes that hyperthyroid cats could serve as modern-day versions of the canaries in the cage that alerted coal miners to poisonous gas.

 

Dr David Obendorf

The chemists also measured PBDEs in 700 samples of farmed and wild salmon from around the world (all except Tasmania), including most major salmon-producing regions. The study, which is by far the largest of its kind, used the same samples from an earlier study that revealed significantly higher levels of organo-chlorine chemicals like PCBs and dioxins in farmed salmon than in wild salmonids. They also reported that with one exception all farm-raised fish samples had much higher levels of PBDEs than wild salmon. They also found that farmed salmon from Europe had higher levels than those from North America, and that both European and North American farm-raised salmon had higher levels than those raised in the southern hemisphere (southern South America - Chile).