On July 24th, 2014, Senator Merkley (D-Oregon) proposed legislation to phase out priority PBT chemicals identified by the USEPA in the next five years. If the bill passes, it would be an incredible step in protecting human health and the environment, as well as meeting the standards of other developed nations. The link below leads you to his press release about the bill:
Below, I summarize what PBTs are, the problems they pose, and current legal standing on PBT chemicals.
Defining persistent bioaccumulative toxics (PBTs) proves a difficult task despite their intuitive name. While they are persistent, bioaccumulative and toxic, the criteria for classifying a chemical a “PBT” are unclear and remains up for debate both domestically and internationally. However, there is consensus that certain chemicals are more dangerous than the generally well-understood “toxic” classification. Many chemicals are seemingly harmless (or, rather, their existence in a living system proves to be negligible) in low quantities, but the chemicals with the capability of remaining in an ecosystem (persistence) or concentrating in an animal’s body (bioaccumulation) pose more of a threat than humankind had once thought. Persistence refers to “the length of time a chemical can exist in the environment before being destroyed (i.e. transformed by natural processes” (40 CFR Part 372). Bioaccumulation is used “to describe the process by which organisms may accumulate chemical substances into their bodies. The term refers to both uptake of chemicals from water (bioconcentration) and from ingested food and sediment residues” (40 CFR Part 372).
There are several different areas of thought on the appropriate approach to defining a chemical as a PBT. Some would argue that chemicals must be reviewed on an individual basis and evaluated by their own properties for the risk potential. Others believe that the definition must be quantifiable so as to prevent inequality in evaluation or reliance on political will for action. For the sake of simplicity, we will define PBTs as the priority substances, or substances of substantial concern, identified by scientists reviewing chemicals based on criteria set by each acting nation or international group. The United States grants the United States Environmental Protection Agency the authority to set US standards for PBT analysis. The USEPA enforces use of PBTs via the Toxics Release Inventory (TRI) Reporting program (USEPA). Currently, the USEPA identifies PBTs based on the following criteria: a half-life greater than or equal to two months in soil, sediment, or water; a half-life greater than or equal to two days in air; and a bioaccumulation factor (BAF) or bioconcentration factor (BCF) greater than or equal to 1000 (or logKow ≥ 1) (1999-10-29 FR). In comparison to international standards, the USEPA’s criteria fall into the median range (“Integrated Approach to PBT and POP…” Wijk 700).
The primary problem posed by PBTs is the effect on human and environmental health. Several infamous chemical substances including Rachel Carson’s DDT (dichlorodiphenyltrichloroethane), mercury, lead, et cetera are classified as PBT chemicals. While the effects of these chemicals have been widely publicized, leading to strong legislative repercussions, many chemicals on the list provided by the TRI program are largely unknown and unaddressed. Chemicals such as kepone (also known as chlordecone), a chemical closely related to DDT, cause damage to the nervous system and fatty tissues required for reproductive capabilities (USEPA). Polychlorinated biphenyls (PCBs) are also included on the list of priority PBTs as they act as a carcinogen, mutating cells that lead to cancer (USEPA). It would appear the answer to this problem is simple—why not eliminate public exposure to these dangerous chemicals altogether? Unfortunately, the economic, political and judicial will to accomplish this task appears to be virtually nonexistent. Additionally, not all of the chemicals are harmful in small doses, which puts EPA in the position of allowing a company to release a quantity that would not be harmful on its own, but when several companies acquire the same release rights, the chemical becomes an aggregate problem. The pain caused by PBTs comes as a result of many players acting in their own interest with no intention of causing a problem. When every company or manufacturer follows suit dispersing the critical load, the case of PBTs becomes a tragedy of the commons.
In 1991, the United States Environmental Protection Agency made its first attempt to entirely ban the use, processing, and manufacturing of a chemical under Section 6 of the Toxic Substances Control Act (TSCA). They strategically chose asbestos because of the clearly established link between asbestos and a lethal lung cancer called “asbestosis” (Corrosion Proof Fittings v. the USEPA). However, the case would end EPA’s hopeful approach to chemical regulation. The presiding judge ruled that the USEPA only had the authority to “apply one or more of the following requirements to such substance or mixture to the extent necessary to protect adequately against such risk using the least burdensome requirements” (Smith Opinion part IV B). This interpretation would force the USEPA to weigh economic benefit against the economic burden caused by a chemical ban. This devastating judicial blow led the EPA to retreat from all further attempts at banning a substance presently used on the commercial market. So, now the problem with PBTs remains in the same limbo-like state as all other TSCA-regulated chemicals being commercially produced—if the USEPA cannot ban a substance, then their only choice would appear to be regulating quantity relative to potential harm. And, while it would seem worthwhile for companies to discontinue the use of dangerous and TRI-listed chemicals, the incentive to end PBT use does not exist as these chemicals are often more useful and cost-effective than their substitutes. The fatal flaw of PBTs is that they work.
TSCA was first passed by Congress in 1976 as the chemical regulatory arm of the relatively new Environmental Protection Agency. Section 2 of TSCA states that Congress created TSCA to effectively regulate chemical substances in order to protect the general public from exposure to “the many chemical substances and mixtures which are constantly being developed and produced, there are some whose manufacture, processing, distribution in commerce, use, or disposal may present an unreasonable risk of injury to health or the environment” (TSCA Sect. 2 (a) 2). While Section 2 (b) 2 seeks to provide the USEPA with adequate authority to regulate, Section 2 (b) 3 almost immediately sacrifices the power to protect for the power to support industry. The ambiguous language used in TSCA, particularly words such as “adequate” or “unreasonable,” allows for industry to fight the USEPA every step of the way, despite the EPA’s responsibility to protect. PBT chemicals, particularly those listed as priorities, present unreasonable risk of injury to health or the environment, so the USEPA must do something to regulate them in a manner suitable to economic growth and industry advancement.
Later in the Toxic Substances Control Act legislation, Congress lays the foundation for the appropriate regulatory steps and gives the USEPA the specific authorities necessary to regulate the chemical market. Section 4 requires the testing of chemical substances and mixtures, Section 5 requires manufacturing and processing notices, and Section 6 gives the USEPA the authority to regulate hazardous chemical substances and mixtures (TSCA). Section 6 also includes the option for labeling new chemicals with special analysis and regulation provisions as Significant New Use Rule chemicals (TSCA). Many US priority PBTs fall into the SNUR categories with exceptions for specific and necessary uses (USEPA). Section 7 of TSCA provides for the seizure (clean-up) of imminent hazards, but Section 7 has never been officially authorized by the USEPA nor does it inhibit or limit chemical use with the precautions necessary to prevent PBT-related harm (Walker; TSCA)
According to Wijk, et al, the USEPA issued a 1999 policy statement for persistent organic pollutant (POPs, a subset of PBTs subject to long-range transport, “Environmental Persistence of Organic Pollutants…” Boethling, et al.) guidance criteria for new chemicals being analyzed for commercial use under TSCA. While the policy remains available online, the POP policy has since been grouped under the TRI program and the PBT website is no longer updated by the USEPA.
EPCRA requires that the USEPA and state regulatory bodies collect information about the release or transfer of chemicals and make the information available to the public through the Toxic Release Inventory (TRI) program (Wijk et al.). In 1999, the USEPA issued a Federal Register memorandum lowering the threshold (under EPCRA and the Pollution Prevention Act) of reporting for substances fitting the PBT criteria (the criteria discussed in the first definitions section is derived from the TRI criteria):
“EPA currently  allows facilities to report whole numbers and to round releases of 0.5 pound or less to zero. EPA explained its concern that the combination of requiring the reporting of whole numbers and allowing rounding to zero would result in a significant number of facilities reporting their releases of some PBT chemicals as zero. EPA, therefore, proposed that all releases or other waste management quantities greater than 1⁄10 of a pound of PBT chemicals (except dioxins) be reported, provided that the appropriate activity threshold has been exceeded. For the category of dioxin and dioxin-like compounds, which have a proposed reporting threshold of 0.1 gram, EPA proposed that facilities report all releases and other waste management activities greater than 100 micrograms (ug) (i.e., 0.0001 gram)” (1999-10-29 FR)
Additionally, the USEPA added the categories of dioxin, with a reporting threshold of 0.1 gram, and vanadium chemicals (1999-10-29 FR).
On the EPA website, persistent organic pollutants are listed as a priority concern and the agency (not the US Senate) has signed on with the members of the Stockholm convention to accomplish the goals of eliminating POP distribution altogether (USEPA).
In the article written by Wijk, et al, he describes the international community’s attempts to standardize definitions and criteria for PBTs due to their ability to travel and negatively impact widespread areas. As a globally active nation with substantial power, the United States maintains responsibilities to protect and interact with the international community. The following paragraphs provide a brief overview of how several nations (North American, European, and Asian) characterize and regulate PBTs:
The European Union created a regulatory program called REACH in 2007. Under REACH, the European Chemicals Agency screens for potential persistence and bioaccumulation using information about “ready biodegradation” and lipophilicity (log Kow).
REACH classifies PBTs using several chemical annexes:
- Annex XIII: analytical criteria for PBT or vPvB properties
- Annex XIV: substances that must be reported before new use or current regulated substances (listed based on Annex XIII and XV criteria)
- Annex XV: special dossier– degradation half-lives, bioconcentration factors (BCFs) from aquatic organisms, and information on toxicity; additional chemicals of concern also analyzed (REACH).
Stockholm Convention is a global treaty to protect human health and the environment from PBT chemicals that are subject to long-range transport, particularly persistent organic pollutants. There are currently twelve POPs listed in the treaty. The United States is one of the few developed nations that has not agreed to eliminate persistent organic pollutants, but the USEPA has signed on as an agency aiming to work towards the international goal (USEPA).
The Stockholm convention lists the chemicals in the following categories, defining the criteria in Annex D:
- Annex A: Elimination
- Annex B: Restriction
- Annex C: Unintentional Production
- Annex D:
- Persistence: 1) evidence that the half-life of the chemical in water is greater than 2 months, > 6 months in soil, > 6 months in sediment 2) evidence that the chemical is otherwise sufficiently persistent to justify its consideration within the scope of the convention
- Bioaccumulation: 1) evidence that the BCF/BAF is > 5000 (or >5 log Kow) 2) evidence that a chemical presents other reasons for concern such as high bioaccumulation in other species, high toxicity, or ecotoxicity 3) monitoring data in biota indicating that the bioaccumulation potential of the chemical is sufficient to justify its consideration within the scope of the Convention
- Adverse Effects: 1) evidence of adverse effects on human health or the environment that justifies consideration of the chemical within the scope of the convention 2) toxicity or ecotoxicity data that indicate the potential for damage to human health or to the environment
- Potential for Long-Range Transport: 1) measured levels of the chemical in locations distant from the source of its release are of potential concern 2) monitoring data showing that long-range environmental transport of the chemical, with the potential for transfer to a receiving environment, may have occurred via air, water, or migratory species 3) environmental fate properties or model results that demonstrate the chemical has a potential for long-range environmental transport, with the potential for transfer to a receiving environment in distant locations from point of origin (Wijk 702)
The Aarhus Protocol on Persistent Organic Pollutants to the 1979 Convention on Long-Range Trans-boundary Air Pollution was officially adopted in 1998. The protocol seeks “to eliminate any discharges, emissions or losses of POPs” (Wijk 700). The protocol has categorized chemicals based on criteria analyzing PBT properties into the following annexes:
- Annex I: Elimination
- Annex II: Restriction on Use
- Annex III: Regulation of Total Annual Emissions (Wijk 700)
Canada’s Toxic Substances Management Policy of 1995 is a policy that “applies to actions undertaken by the Government with regards to chemical substances… the policy provides for the virtual elimination of anthropogenic toxic substances or other anthropogenic substances of concern that meet the criteria for persistence and bioaccumulation and that are not naturally occurring radionuclides or inorganic substances” (Wijk et al. 698). The TSMP provides the basis for further action regarding the removal of PBTs from Canadian industry.
Canadian Environmental Protection Act of 1999 “require[s] the systematic review of substances in commerce, as listed on the Domestic Substances List (DSL) to determine which met criteria for persistence, bioaccumulation and inherent toxicity (iT) or were deemed to pose the greatest potential for exposure to humans” (Wijk et al. 698). CEPA includes two specific provisions to regulate chemicals:
- The Domestic Substances List includes “approximately 3250 substances [that] met the criteria as 1) either persistent or bioaccumulative and 2) inherently toxic to aquatic organisms.” The DSL named two-hundred high priority substances, one-hundred and thirty of which met all of the PBT criteria. (Wijk et al. 698)
- Significant New Activity provisions require “that anyone proposing to reintroduce a given substance into Canadian commerce submit additional information that would allow further assessment and regulatory consideration of appropriateness” (Wijk et al. 698).
Despite less stringent classification standards, Canada has publicly listed significantly more chemicals than the United States. It is important to note, however, that the US only lists those chemicals that fit into all categories while Canada is also listing chemicals that are simply very persistent and/or very bioaccumulative (vPvB) (Boethling, et al.).
The Chemical Substances Control Law of 1973 introduced a “ban on the production and use of PBT substances, restriction and labeling of persistent and toxic substances, notification of production of substances of concern, and notification and evaluation of new substances for PBT properties.” This law was one of the first laws established in regards to PBT chemicals. The law includes two classifications:
- “Class I (16 substances in 2009): persistent, bioaccumulative and hazardous chemicals with long-term human toxicity or ecotoxicity to higher predators. None of these substances have a virtual ban on production and use.
- Class II (23 substances in 2009): persistent, hazardous and with a concern about long-term presence in the environment. There are restrictions on the production and use of these substances, such as limits on production volumes or labeling requirements.” (Wijk et al)