The US EPA should not use the approach outlined in its TSCA systematic review document for the five 'PBT' substances that will be subject to expedited risk management action, according to comments from NGOs.
The Lautenberg Act, which amended TSCA in 2016, requires the EPA to take quick or "expedited" action on certain substances that are persistent, bioaccumulative and toxic (PBT). The law directs the EPA to skip risk evaluation of these substances and proceed directly to imposing rules to reduce their exposure "to the extent practicable".
The five substances are:
- hexachlorobutadiene (HCBD);
- pentachlorothiophenol (PCTP);
- tris(4-isopropylphenyl) phosphate (IPTPP); and
- 2,4,6-tris(tert-butyl) phenol (2,4,6-TTBP).
In comments submitted in response to two EPA documents that analyse their uses, exposure routes and hazards, NGOs and academics have remained strongly critical of the EPA's systematic review document. This recently released guidance outlines the approach the EPA will take to integrating data from multiple sources, a key step in risk assessment of data-rich substances.
"The document is incomplete, inconsistent with the state of the science, and too flawed to be used," said the Natural Resources Defense Council in its comments. "Accordingly, use of the document violates TSCA and is otherwise arbitrary and capricious."
The NRDC said that it was "particularly concerned" about the use of the document for assessment of the five PBT substances. Its comments – dated 16 August but posted to the public docket this month – were supported by 19 other organisations.
The concern about use of the systematic review document for assessment of the five PBT substances was echoed in comments from Safer Chemicals Healthy Families (SCHF) and a group of 33 scientists, including ten from the University of California.
The NGOs also criticised the EPA for failing to account for many routes of exposure and for dismissing a large volume of exposure data.
The "principle concern" of the SCHF, however, was was that the EPA had not clearly explained how the two documents on the five PBT substances will influence restriction of the substances under TSCA section 6(h)
"It’s critical that the agency has a clear understanding of the goals and requirements of section 6(h) and how the two documents will contribute to meeting them," it said.
The American Chemistry Council, meanwhile, described as "problematic" the proposed use of read-across for exposure assessment of the antioxidant 2,4,6-TTBP.
"We commend the extension of this principle [of read-across] to the area of exposure characterisation," the trade association said. "However, EPA has not identified those characteristics that would make a surrogate chemical suitable for read-across for exposure."
It also recommended against the proposed use of exposure data from outside the US and from studies that have not been put in their "temporal context" with respect to substance use trends.
Proposed risk management rules for all five substances are due by 22 June 2019. Final rules are set to follow within 18 months.