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
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