Manganese Neurotoxicity: Applying Epidemiological Results to the General Population.

Expert Meeting, Dec. 5 and 6, 2002
Report Summary¹

Table of Contents

• Background
• Health Canada staff in attendance
• Discussions - Part 1 - (Questions 1 and 2)
• Discussions - Part 2 - (Questions 3,4,5,6 and 7)

Background

Due to the substantial body of new information on manganese that had become available since its 1994 risk assessment², Health Canada began preparations in 2002 to revisit the risk assessment, beginning with preparation of a review of all recent epidemiological literature. Health Canada then hosted a meeting of experts in manganese neurotoxicity in order to determine the state of scientific knowledge on several issues directly relevant to risk assessment, and to seek guidance on how to interpret the primarily occupational results (mostly from young healthy adult males) in terms of the implications for the general population (which includes the very young, the elderly and other subpopulations of varying degrees of sensitivity).

A reference concentration for airborne manganese of 0.11 mg/m³ was established by Health Canada in 1994, and current risk assessment activities will result in confirming that guideline or developing a new one. Panel members were asked for their input on the significance of the health endpoints, and on additional qualitative evidence available to support any quantitative risk assessment. They were also asked to consider other points, including the enhanced sensitivity of various subpopulations, and what exposure metric(s) and time frame would provide optimum protection from the health effects of manganese.

Expert panel members were selected to provide a broad range of expertise, including neurology, medical epidemiology, occupational hygiene, research toxicology, and risk assessment. The expert panel consisted of:

Harry Roels, Université catholique de Louvain, Belgium. Occupational hygienist and epidemiological researcher, working for many years assessing workers exposed to manganese and other industrial chemicals. His neurological testing work on Belgian battery plant workers was used for risk assessment purposes by four agencies, including Health Canada, the United States Environmental Protection Agency (US EPA), and the World Health Organization (WHO), as well as two private U.S. companies.

Donna Mergler, Université de Québec à Montréal. Primary interest in neurotoxicity related to environmental pollutants, and principal investigator of both an occupational and a general population study of manganese neurotoxicity in/near an industrial plant near Montreal. Her experience with the effects of manganese in the general population was of particular interest to the discussions.

Roberto Lucchini, University of Brescia, Italy. Medical epidemiologist; principal investigator in several recent epidemiological investigations of workers in a ferromanganese alloy plant in northern Italy, as well as current involvement in a study of inhabitants of a valley with high industrial emissions of manganese, with respect to the prevalence of parkinsonism.

Oksana Suchowersky, University of Calgary. Clinical neurologist, with expertise in movement disorders. She does both clinical and research work on Parkinson's Disease and other related disorders. Her perspective on the gradient from severe parkinsonian symptoms to the subclinical effects of manganese was sought by other meeting participants.

David Bellinger, Children's Hospital, Boston. Neurologist and epidemiologist; principal investigator in a key longitudinal study on the effects of prenatal lead exposure on subsequent mental development in children. He has also written about the interpretation of small health deficits at the individual level, their implications for the population as a whole, and their integration into risk assessment.

Mike Davis, US EPA, Office of Research and Development. Risk assessor, lead author for the U.S. EPA 1994 health risk assessment of inhaled manganese, and prepared the background document for the WHO European air quality guideline for manganese.

Grace Wood, retired, formerly Health Canada, Environmental Health Directorate. Co-author of the 1994 risk assessment and author of the newer epidemiological review sent to meeting participants. Responsible for fuel issues at Health Canada, including both lead and manganese, from 1985 to 1998.

Health Canada staff in attendance were:

Barry Jessiman, meeting Chairman. Health Canada, Head, Air and Fuel Risk Assessment Section, with overall responsibility for development of risk assessments for various air pollutants.

Marika Egyed, Health Canada, Air and Fuel Risk Assessment Section, working on fuel issues, co-author of the 1994 manganese health risk assessment, currently working on manganese.

Mike Inskip, Health Canada, Environment and Occupational Toxicology Division. Experimental toxicologist; has worked extensively in research on other neurotoxicants, specifically lead and methyl mercury in primates.

Jill Kearney, Health Canada, Air Health Effects Division. Involved in exposure assessment science, in both risk assessment and research projects. She is conducting research on characterizing particulate matter (PM) in a city with large industrial sources of manganese and in another large urban centre.

Wayne Bowers, Health Canada, Environment and Occupational Toxicology Division. Experimental toxicologist, involved with neurological research dealing with pesticides, PCBs and mercury.

Mike Walker, Health Canada, Biostatistics Division. Involved in many quantitative risk assessments done within the Environmental Contaminants Bureau of Health Canada.