Summary of Public Comments received on the Challenge substance Carbon Black (Chemical Abstract Service Registry Number: 1333-86-4) Draft Screening Assessment Report for Batch 12

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Comments on the draft screening assessment report for Carbon Black to be addressed as part of the Chemicals Management Plan Challenge were provided by the International Carbon Black Association.

A summary of comments and responses is included below, organized by topic:

Topic Comment Response
Risk Assessment The concentration used in the draft human health assessment should not be taken as the Lowest-observed-effect-concentrations (LOEC) for chronic exposure to carbon black; in the key study by Gardiner et al. (2001), effects were related to long-term cumulative exposure, rather than the current exposure which is the basis for the LOEC used. In addition, the questionnaire data on respiratory symptoms were unreliable. 

In the final screening assessment for carbon black, we have retained the LOEC of 0.57 mg/m3 from Phase 3 of the study by Gardiner et al., for the following reasons: (1) in this study, both current and cumulative exposure were related to health effects; (2) this LOEC yields the most health-protective Margin of Exposure, which is consistent with the requirement under CEPA to apply the precautionary principle in assessments; (3) using this LOEC was suggested by all of the external peer reviewers of the draft assessment.

It is true that there were differences in the way that the questionnaire data were collected between factories in the key study.  However, the authors took these differences into account by including “factory” as a variable in the regression models.  In addition, the effects observed were not restricted to symptoms, but also included declines in several measures of lung function.

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