More words minced this time, but EPA’s science advisors raise serious concerns with its draft risk evaluation of 1-bromopropane

Richard Denison, a Lead Senior Scientist.

The peer review report by the Scientific Advisory Committee on Chemicals (SACC) on EPA’s draft risk evaluation of 1-bromopropane (1-BP) has been released.  This carcinogenic solvent is one of the first 10 chemicals undergoing risk evaluation under the amended Toxic Substances Control Act (TSCA), and the new SACC report covers the fourth of EPA’s draft risk evaluations (DREs) to be peer-reviewed.  We’ve blogged earlier about the SACC’s reports on EPA’s draft risk evaluations for 1,4-dioxane and HBCD and Pigment Violet 29.

At first blush, the new report reads less harshly than the last one, and the SACC notes clear improvements in the content and organization of the 1-BP draft over earlier ones.  But even the Executive Summary raises quite scathing criticisms that go to the heart of whether EPA has developed sufficient data to support its risk determinations for this chemical.  Here is a telling excerpt (p. 17, emphases added):

Overall, the Committee concurred that even though data provided in the DRE underestimated risk, these data did support the finding of unreasonable risk to consumers and occupational conditions, including occupational non-users. Conversely, inadequate data were presented for a robust risk characterization for the environmental assessment, and the information provided did not support the conclusion of “no unreasonable risk to the environment.”

These conclusions mirror those drawn by EDF in the comments we submitted to EPA on the 1-BP DRE.

Themes sounded by the SACC in its earlier peer reviews came up again here. 

Exclusion of exposures from environmental releases:  With regard to EPA’s wholesale exclusion of exposures to the general population from 1-BP’s releases to air, water, and land, the SACC had this to say (p. 17, emphases added):

The lack of consideration for general population exposures excludes a vast extent of the US population (workers, consumers, school children, and other populations) who are exposed to 1-BP, perhaps on a daily basis. The lack of consideration of the general population exposure is concerning given the strong evidence of widespread exposure to a chemical that may be 1-BP based (from biomonitoring data). Many of these problems stemmed from a reduction in the Scope of this assessment during the time since the 2016 Draft Problem Formulation. Many members of the Committee found this reduction in scope troubling.

Unwarranted assumptions underestimating risk to workers:  EPA’s assumption of universal, effective use of personal protective equipment (PPE) by workers as a basis to ignore the risks workers face was again heavily criticized by the SACC:  “[T]he assumption that Personal Protective Equipment (PPE) would be used consistently and by all workers is overly optimistic and the draft risk evaluation provided no data to support these assumptions” (p. 16).

The SACC particularly took EPA to task for its failure to consider the combined exposures to the same individuals, which EPA only considered in isolation from each other.  Said the SACC:  “[A] worker who is occupationally exposed may also be exposed through other conditions of use in the home. Yet, these exposures are decoupled in the draft risk evaluation” (p. 16).  And, in a case of being about as nice as it could possibly be, the SACC noted that “inclusion of an estimate of combined oral and dermal exposure would be welcome” (p. 14).

Inadequate evaluation of risks to vulnerable subpopulations:  The SACC notes that “consideration of potentially exposed or susceptible subpopulations (PESS) under TSCA is new and challenging” but makes clear that it “considers the approach in this draft risk evaluation to be inadequate to address PESS risk” (p. 15).

Omission of key hazards and risks:  The SACC flagged EPA’s omission of any consideration of neurotoxicity and immunotoxicity, indicating EPA had not provided sufficient justification for excluding these human health endpoints (p. 15).  Likewise, the SACC flagged EPA’s failure to consider cancer risks from short term exposures (p. 15).

The SACC also noted the “paucity of data for the environmental assessment” (p. 16), including no data on reproductive or developmental toxicity, and recommended EPA at a minimum include additional uncertainty factors.

Systematic review:  The SACC identified numerous inconsistencies in evaluating, and inadequate justifications for excluding, many studies evaluated using the TSCA systematic review approach (pp. 12, 16, 19-26).  The SACC noted that “[f]ewer than 25% of the references cited in the DRE were evaluated for data quality” (p. 23).  Once again the SACC urged EPA to submit its approach for third-party review, a step EPA finally took late last week.


The SACC did note the hard work that EPA career staff have been devoting to these draft risk evaluations, and noted the challenges they entail, a sentiment we certainly echo.  At the same time, the SACC’s report again makes clear that unfounded assumptions, questionable policy decisions, and suspect methodological choices are leading EPA to systematically underestimate risks of the chemicals it is evaluating under TSCA.


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