Polybrominated Diphenyl Ethers (PBDEs)

Toxic Sewage Sludge, the solids separated from raw sewage in a Wastewater Treatment Plant (WWTP), accumulates and retains the physical materials, chemical wastes and microbial constituents from all sources that contribute to raw sewage inflows. Toxic chemicals from domestic, medical, industrial and stormwater runoff sources represent some of the Persistent Organic Pollutants (POPs), Chemicals of Emerging Concern (CECs) and Persistent, Bioaccumulative Toxics (PBTs) found in Toxic Sewage Sludge.

 

Each observed particle, fiber, hair, metal, plastic, fragment or other observed material represents a source of toxics in sewage sludge that is land-disposed in forests and on farms

Many hundreds of Synthetic POPs, CECs and  PBTs are known to accumulate in Sewage Sludge, including Brominated Flame Retardants (BFRs, Polybrominated Diphenyl Ether Flame Retardants [PBDEs]), Nonylphenols (NPs), Polychlorinated Biphenyls (PCBs), Organochlorine Pesticides (OCPs), Pharmaceutical and Personal Care Products, and many other categories of toxic chemicals. Further, more than 70% of the toxic chemicals detected in Sewage Sludge are also detected in humans.

 

It is what cannot be seen that is most toxic and dangerous in sewage sludge. Many toxic chemicals are bound to the plastics that can be seen, ready to release to the environment.

WWTPs degrade much of the organic matter in raw sewage by microbial digestion. However, screening, settling, filtration and dewatering assure that most of the residual physical materials and the poorly-degraded or newly-generated and novel toxic chemicals partition to the solid phase, i.e., to the Toxic Sewage Sludge that is destined for land disposal in forests and on farms and rangelands.

 

The chemical reactions that occur in raw sewage inflows, in the wastewater processing steps and in the semi-liquid sewage sludge product environment yield novel toxics, many of which remain uncharacterized, and definitely not subjected to any safety/toxicology testing. The toxic effects of exposure to sewage sludge are real, yet the sources of the toxics and the clinical manifestations of the toxicities remain unknown.

What fate awaits the toxics?

 

Toxic Sewage Sludge is disposed in forests and on farms and rangelands, but the associated toxicities remain generally uncharacterized. Some plants survive toxic exposure. Deep applications of Toxic Sewage Sludge favor anaerobic microbes that generate substantial amounts of Methane, Nitrous Oxides, Carbon Dioxide and other Greenhouse Gasses, as well as novel toxics for which analytical methods have never been developed. What are they, and what do they do?

Components of Toxic Sewage Sludge that are not degraded in a WWTP are mostly land-disposed, and thereafter they partially or fully degrade (or not) as a function of their chemistry and the local environment. The resulting degradates (degradants, decomposition products) are released from the parent compounds by any of several mechanisms, contributing further to environmental toxicity. Independently or in concert, the processes of oxidation and microbial degradation often yield wholly unanticipated toxics new to the air, land, water and biotic environments.

 

While many plants in the forests are killed rapidly by exposure to Toxic Sewage Sludge, a select list of forest fungi thrive on the toxics, perhaps by using certain toxics as nutritional substrate, or perhaps by defense mechanism not yet investigated.

It is important to remain aware that: Nearly all chronic diseases are caused by the cumulative effects of long-term exposure to low levels of environmental contaminants and pollutants. In a Toxic Sewage Sludge-strewn environment, the sources are not mysterious.

Toxic Sewage Sludge from WWTPs holds examples of most classes of toxic pollutants, including the POPs, CECs and PBTs, with hundreds of synthetic members of these groups known to accumulate in the sludge solids.

Common plastics, such as Low-Density Polyethylene, form the basis of a vast plastics industry, including use in Pharmaceutical and Personal Care Products; they are natural accumulators of toxic chemicals, including Brominated Flame Retardants, and especially the Polybrominated Diphenyl Ethers, as well as the highly toxic Organochlorine Pesticides, Nonylphenols, Dioxins, Furans and Polychlorinated Biphenyls. These are some of the highest priority toxic chemicals encountered in any domestic, medical, industrial or agricultural wastewater stream. The presence of these toxics in raw sewage, and then in the wastewater treatment process, assures their contribution to the priority toxic chemicals in wastewater, plus their ultimate partitioning and accumulation in the resulting Toxic Sewage Sludge product.

Polybrominated Diphenyl Ethers (PBDEs) are synthetic flame retardants used in a variety of consumer products, including polyurethane foams, fabrics, and plastics (https://wsp.arizona.edu/node/251). Because of stringent requirements for product flame resistance, PBDE usage in the United States is the highest of any country in the world. PBDEs have been detected in household dust, and their ubiquitous presence has been hypothesized as the reason for their introduction into municipal wastewater. PBDEs are hydrophobic; they partition strongly to biological solids and they accumulate in biosolids produced during wastewater treatment. … the fate of PBDEs after land application is a question of broad environmental interest. There is concern that PBDEs may produce adverse health effects among exposed wildlife and humans. They are known endocrine disrupting compounds that interact with both the estrogen and thyroid hormone systems.”

 

Toxic Sewage Sludge samples collected from a forest land-disposal site for analysis.

 

Sewage Leachate sample collected from a sewage sludge leachate puddle directly adjacent to a land-disposed sewage sludge site in the Snoqualmie Forest of eastern King County, WA.

Analysis of forest-disposed Toxic Sewage Sludge (King County, WA, WWTP, 2015) and receiving leachate puddles and runoff waters collected from a Snoqualmie Forest sewage sludge disposal site.

Analytical chemistry results reveal the menu of toxic flame retardants and triclosan detected in the sewage sludge and outflow leachates and runoff (Table below).

Control samples of air, soil and water from a directly adjacent area that did not receive sewage sludge showed no evidence of the compounds detected in the sewage sludge and water samples.

Sewage Sludge-Borne Flame Retardants and Triclosan Detected in Forest-Disposed Sludge

It is notable that Pentabromodiphenyl ether (BDE-85) was eliminated from production under the Stockholm Convention, a treaty to phase-out POPs. It is found at elevated concentrations in air, water, soil, food, sediment, sewage sludge and dust; it enters the body by ingestion or inhalation; it is stored in body fat, and it is retained in the body for years.

PDE-47 and PDE-99 accumulates in terrestrial carnivores and humans at rates higher than any other industrial chemical.

Tris (1,3-dichloroisopropyl) phosphate (TDCPP) is a chlorinated organophosphate, various forms of which are used as flame retardants, pesticides, plasticizers and nerve gases.

More than 70% of toxic chemicals detected in sewage sludge are also detected in humans. They concentrate in sewage sludge, are persistent in the environment, bioaccumulate in fatty tissues, have degradation products with elevated toxicity, and are synthetic, rarely occurring as single compounds.

Until these toxic chemicals can be eliminated from raw sewage and other wastewater streams, it will be important to expand testing of all sewage sludges and wastewater effluents to assure that the risk and threat may be determined and the public placed on alert.

 http://www.ncbi.nlm.nih.gov/pubmed/24091190

 http://www2.dmu.dk/1_Viden/2_Publikationer/3_Fagrapporter/rapporter/FR481.PDF