Screening assessment report for chlorinated naphthalenes: chapter 2

Introduction

The Canadian Environmental Protection Act, 1999 (CEPA) requires the Minister of the Environment and the Minister of Health to conduct screening assessments of substances that meet specified criteria to determine whether these substances present or may present a risk to the environment or human health. Based on the results of screening assessments, the ministers have several options: they may propose to take no further action with respect to substances; they may suggest adding substances to the Priority Substances List for further assessment; or they may recommend adding substances to the List of Toxic Substances in Schedule 1 of the act and, when applicable, taking steps to virtually eliminate them.

Screening assessments involve analyzing available information about substances using reasonable worst case assumptions to determine whether the substances are "toxic" or capable of becoming so, as defined in CEPA. During screening assessments, various pieces of scientific and technical information are examined and conclusions are developed based on the weight of evidence and on the precautionary principle, as required under section 76.1 of CEPA. Screening assessments do not present an exhaustive review of all available data; rather, they present the most critical studies and lines of evidence pertaining to the conclusions.

A screening assessment of chlorinated naphthalenes (CNs) was undertaken in part because "Naphthalene, chloro derivatives", Chemical Abstracts Service Registry Number 70776-03-3, was identified as a high priority for assessment of ecological risk as it had been found to meet the categorization criteria including persistence (P), bioaccumulation potential (B) and inherent toxicity to aquatic organisms (iT). "Naphthalene, chloro derivatives" can be described as a variable chemical mixture that covers the chemical class of CNs. Additionally, CNs were assessed because their production and usage have been banned or restricted in various OECD (Organisation for Economic Co-operation and Development) countries, including Switzerland, Germany and Japan. As well, recent scientific studies indicated the presence of CNs in the Arctic and Antarctica, suggesting that CNs are persistent in air and subject to long-range atmospheric transport.

Although CNs were found to be a high priority for assessment with respect to the environment, they did not meet the criteria for greatest potential for exposure or intermediate potential for exposure, and were not identified as posing a high hazard to human health, based on classifications by other national and international agencies for carcinogenicity, genotoxicity, developmental toxicity and reproductive toxicity. Therefore, this assessment focuses on information relevant to the evaluation of ecological risk.

The number of chlorine atoms within the CN structure is a key determinant of a CN's physical and chemical properties. Consequently, the potential for each CN homologue group to cause environmental harm is evaluated separately in this report. Furthermore, because of the unique concerns relating to substances that are persistent and bioaccumulative, and given that current science is unable to accurately predict the ecological effects of such substances, the assessments of the CN homologue groups with these properties were performed using a less quantitative, more conservative (precautionary) approach than might otherwise have been taken.

Data relevant to the screening assessment of CNs were identified in original literature and review documents that summarize current scientific information about them (for example, International Programme on Chemical Safety (IPCS) Concise International Chemical Assessment Documents (CICAD) No. 34: Chlorinated Napthalenes (IPCS 2001)). Searches of online literature databases were conducted. As well, direct contacts were made with researchers, academics and industry to obtain information about CNs.

Scans were conducted of the open literature, conference proceedings and the Internet for relevant information. Data obtained up to September 2007 were considered in this document. In addition, a voluntary industry survey about CNs was conducted by Environment Canada in 2003, to collect data on the Canadian manufacture, import and use of CNs.

This screening assessment report and the associated unpublished working documentation were written by Environment Canada evaluators in the Ecological Assessment Division in Gatineau, Quebec. The information in this report was reviewed by Canadian and international experts from government, industry and academia. However, the conclusions are those of Environment Canada and do not necessarily reflect the opinions of the external reviewers.

Supporting working documentation is available upon request by email. Information on screening assessments under CEPA is available on the Chemicals Management Plan web section.

The critical information and considerations on which the assessment is based are presented below.