Ecology's PBT Initiative

The PBT List - What is it?

The PBT List comes from the PBT Rule and contains 25 chemicals and chemical groups, and 2 metals of concern. The chemicals on this list meet the criteria of “persistence”, “bioaccumulation”, and “toxicity” as defined in the PBT Rule. The purpose of the PBT List is to identify toxic chemicals that require special action because they remain (persist) in the environment for long periods of time where they build up in humans and animals to levels that pose threats to human health and the environment in Washington (bioaccumulate).

How do we choose the chemicals on the PBT List?

Ecology screened several chemicals, chemical groups and metals in order to determine if they meet or exceed the following criteria:

For Persistence– if half the amount of the chemical or chemical group can remain in unchanged form in soil, sediment or water for more than 60 days; AND
For Bioaccumulation – if the chemical or chemical group’s bioconcentration factor or bioaccumulation factor in aquatic species is greater than 1000. This means that the concentration of a chemical in an aquatic animal is 1000 times or more the concentration of that chemical in the surrounding water. (or in the absence of such data, has a log-octanol water partition coefficient of greater than 5); AND
For Toxicity – if the chemical or chemical group has the potential to be toxic to humans or plants and wildlife based on credible information that the chemical (or chemical group) [is]:
- Causes cancer; or interferes with development or reproduction; or is toxic to the nervous system;
- Has a reference dose or equivalent toxicity measure of less than 0.003 mg/kg/day. The reference dose is an estimate of daily exposure to humans that is not likely to be harmful. An amount of 0.003 mg/kg/day is very small—about three parts in a billion ; or
- Has a chronic No Observed Effect Concentration (NOEC) of less than 0.1 mg/l or acute NOEC of less than 1.0 mg/l. This means that the substance does not cause low-level, harmful effects in small amounts – less than one-tenth part per million – or larger harmful effects in an amount less than one part per million.

If a chemical or chemical groups meets or exceeds all three of these criteria, according to the PBT Rule, these chemicals are considered to be PBTs.

For metals, if the metal is likely to be present in forms that are bioavailable (or can be taken up by organisms), that metal can also be considered a PBT. An example of this on the PBT List is methylmercury.

Finally, Ecology must consider both the parent chemical and other chemicals it breaks down into (called “degradation products”) when evaluating the PBT criteria. If the parent chemical meets or exceeds the PBT criteria, then both parent chemical and degradation products are considered PBTs.

How do we choose metals for inclusion on the Metals of Concern List?

Metals, unlike chemicals, are naturally occurring substances. However, since some metals are PBT’s many federal and state level environmental programs need to make decisions on whether and how to regulate [metals] them. These decisions include: [range from]

Setting standards or issuing permits for releases of the metal to the environment.
Establishing safe levels of the metal in different environmental media, such as soil or sediment,
Setting priorities for agency programs or voluntary efforts.

In an effort to assist with federal and state decision-making in this area, the US Environmental Protection Agency (EPA) developed the draft Framework for Inorganic Metals Risk Assessment to help determine which metals pose a special health risk. While EPA completes its Framework, Ecology has established a “metals of concern” category in the PBT Rule as an “interim” category and identified two metals of concern. Using the PBT Rule ,Ecology determined that the metals lead and cadmium pose special threats to human health and the environment in Washington.

What PBTs and Metals of Concern are identified in the PBT Rule?

The following chemicals and chemical groups are on the PBT List, as well as two metals of concern:

Chemicals and Chemical Groups on the PBT List and the Metals of Concern List.

Metals	Flame Retardants	Banned Pesticides	Organic Chemicals
Methyl-Mercury	PBDEs Tetrabromobisphenol A Hexabromocyclododecane Pentachlorobenzene	Aldrin/Dieldrin Chlordane DDT/DDD/DDE Heptachlor Epoxide Toxaphene Chlordecone Endrin Mirex	1,2,4,5-TCB Perfluoro-octane sulfonates Hexachlorobenzene Hexachlorobutadiene Short-chain chlor paraffin Polychlrned Naphthalenes
Combustion Byproducts	Banned Flame Retardants	Banned Organic Chemicals	Metals of Concern
PAHs PCDD PCDF PBDD/PBDF	Hexabromobiphenyl	PCBs	Cadmium Lead

How does Ecology intend to use the PBT List?

Ecology will use the PBT List in the following ways:

To select chemicals for chemical action plans.
To do sampling and studies of the environment. The PBT List helps Ecology know what to sample for.
To conduct biomonitoring. The Department of Health does sampling to find out if PBTs on the List are showing up in our bodies.
To increase public awareness about the problems associated with PBTs and the steps that individuals and organizations can take to reduce the threats from PBTs.

A brief description of each chemical or chemical group or metal of concern is provided:

Metals

Methylmercury (Hg) – thermometers, thermostats, fluorescent lamps, coal and petroleum emissions.

Organic Chemicals

1,2,4,5-Tetrachlorobenzene – degradation product of pentachlorobenzene and hexachlorobenzene. Used as a solvent in the manufacturing of dyes, and as a lubricant and degreasing agent.
Hexachlorobenzene (HCB) – No commercial use in US, HCB currently formed as an inadvertent by-product in the production of silicone products, metal cans (surface coating), pesticides, chlorine, and in other chlorination processes. HCB is released from publicly owned treatment works, commercial refuse systems, and petroleum refineries. The use of chlorinated organic compounds in the production of microchips by aluminum plasma etching is also known to generate HCB wastes.
Hexachlorobutadiene – used as a chemical intermediate in the manufacture of rubber compounds.
Perfluorooctane Sulfonates (PFOSs) – used in textile, carpet and leather protection, metal plating, paper and paper packaging, fire fighting foams, industrial and household cleaning products, coatings and coating additives, photographic industry, photolithography and semiconductors, and as a hydraulic fluid in the aviation industry.
Polychlorinated Naphthalenes (PCNs) – not currently used in industry. In past used as a wood preservative, as an engine oil additive, and in electroplating and dye production.
Short-chained chlorinated parraffins (SSCPs) – used in metal working fluids, as plasticizer in paints, coatings and sealants, and a flame retardant in rubbers and textiles, and in leather processing.

Flame Retardants

Polybrominated Diphenyl Ethers (PBDEs) - added to plastics, upholstery fabrics and foams in products as common as computers, TVs, furniture and carpet pads.
Tetrabromobisphenol A – used as a flame retardant in epoxy, vinyl esters and polycarbonate resins, and in polymers such as ABS polystyrenes, phenolic resins, adhesives, paper, and textiles.
Hexabromocyclododecane – used primarily in expanded polystyrene foams and other styrene resins.
Pentachlorobenzene – formerly used as a fungicide and as a flame retardant. Is an impurity of up to 2% in hexachlorobenzene.

Banned Pesticides

Aldrin/Dieldrin – soil insecticide. Banned 1974.
Chlordane – plant insecticide used on vegetables and fruits. Banned 1976.
Chlordecone – chlorinated insecticide used on tobacco, banana and citrus trees. Banned in 1978.
DDT/DDD/DDE – chlorinated insecticide used in [agricultural] agriculture and to control malaria, typhus, and other insect-transmitted diseases. Banned in 1973.
Endrin – soil insecticide used to control corn root worms, beetles, termites, and ants. Banned in 1976.
Heptachlor/Heptachlor Epoxide - soil insecticide used to control corn root worms, beetles, termites, and ants, and control mosquitoes and tsetse flies. Banned in 1988.
Mirex – insecticide used for fire ant control. Banned in 1978.
Toxaphene - chlorinated insecticide used on cotton, cereal grains, nuts and vegetables and to control ticks and mites in livestock. Banned in 1980.

Combustion By-Products

Polybrominated dibenzo-p-dioxins and dibenzofurans (PBDDs/PBDFs) – unintentional by-products in various chemical processes, and from combustion or photolytic degradation of PBDEs and bromophenols.
Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs) – indoor/outdoor fires, forest fires, industrial emissions, waste incineration, auto exhaust.
Polynuclear aromatic hydrocarbons (PAHs) – Used motor oils, indoor/outdoor fires, residential wood stoves, auto exhaust, creosote wood treating, asphalt and coal tar production, coke ovens, meat charbroilers.

Banned Flame Retardants

Hexabromobiphenyl – formerly used as a brominated flame retardant[s] in synthetic fibers and molded plastics. Production ceased and chemical banned in 1974.

Banned Organic Chemicals

Polychlorinated biphenyls (PCBs) – coolant and lubricant in transformers, capacitors and light ballasts. PCBs were banned in 1977.

Metals of Concern

Cadmium (Cd) – used a protective plating for steel, a stabilizer for vinyl chloride, [as] a piment in plastics and glass, [as] a component in various alloys, and in Ni-Cad batteries.
Lead (Pb) – used in the production of batteries, ammunition, metal products (solder and pipes), and devices to shield x-rays. (Due to health concerns, lead in gasoline, house paints, and ceramic products has been dramatically reduced in recent years.)

For further information, contact:

Mike Gallagher
Ecology PBT Coordinator
Solid Waste & Financial Assistance Program
Department of Ecology
PO BOX 47600
Olympia, WA 98504-7600

Phone: (360) 407-6868
Email: MGAL461@ecy.wa.gov