State of the Science Report for 101-14-4 MBOCA

Introduction

Under the Canadian Environmental Protection Act, 1999 (CEPA 1999) the Minister of Health may gather information, conduct investigations and evaluations, including screening assessments, relevant for the purpose of assessing whether a substance is entering or may enter the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.

Screening health assessments focus initially on conservative assessment of hazard or effect levels for critical endpoints and upper-bounding estimates of exposure, after consideration of all relevant identified information. Decisions based on the nature of the critical effects and margins between conservative effect levels and estimates of exposure take into account confidence in the completeness of the identified databases on both exposure and effects, within a screening context. Additional background information on screening health assessments conducted under this program is available at http://www.hc-sc.gc.ca/ewh-semt/contaminants/existsub/index_e.html.

A State of the Science Report for a screening assessment has been prepared on 4,4'-Methylenebis(2-chlorobenzenamine) (MBOCA) (see Figure 1) on the basis that this compound was included in the Domestic Substances List pilot phase for screening as a substance likely to be prioritized on the basis for meeting the criteria for persistence and/or bioaccumulation and inherent toxicity to non-human organisms.

This draft State of the Science Report for a screening assessment and associated unpublished supporting working documentation were prepared by evaluators within the Existing Substances Division of Health Canada; the content of these documents was reviewed at several meetings of senior Divisional staff. The draft Report was subsequently externally reviewed for adequacy of data coverage and defensibility of the conclusions. The supporting working documentation is available upon request by e-mail from ExSD@hc-sc.gc.ca

Information identified as of October 2003 was considered for inclusion in this Report. The critical information and considerations upon which this Report is based are summarized below. Additional data identified between this date and the end of the external peer review period (April, 2004) were also scoped and determined not to impact upon the conclusions presented here.

Identity, Uses and Sources of Exposure

Based on submissions made under Section 71 of CEPA 1999, there were no manufacturers of MBOCA in Canada in the year 2000. The total quantity of MBOCA imported into Canada in 2000 ranged from 100 000 kg to 1 000 000 kg (Environment Canada, 2001). MBOCA is used principally as a curing agent for polyurethane prepolymers in the manufacturing of high-performance, specialized, castable urethane rubber products. Other p otential uses in Canada include mouldings such as industrial tires and rollers, shock absorption pads and conveyor belting (IARC, 1993). MBOCA may also be used in the production of sport boots and shoes, roller skate wheels, cameras, computers, reproducing equipment, home appliances, electrical components and other wear-resistant industrial products (Rozinova et al., 1998; U.S. EPA, 1999). Curing agents, such as MBOCA, will be incorporated into the stable matrices of the cured polymers. Although trace amounts of unreacted MBOCA may be present in consumer products manufactured from polyurethane resins, no data have been identified on potential concentrations. Its high molecular weight and low volatility indicate that the rate of migration of any unreacted MBOCA to the surface of the polymer where consumer exposure would occur is expected to be very low. Potential exposure for the general population of Canada is expected to be as a result of industrial releases.