Wood preservation facilities, general recommendations: chapter A-4

4. Human Health Concerns

The primary safety objective of the industrial use of any chemical or preservative is to minimize worker exposure, ideally so that natural intake levels are not exceeded. If safeguards are not provided or implemented, a variety of human health effects may occur depending on the duration and manner of exposure, concentration of chemicals, chemical forms (valence), and the varying metabolic sensitivities of individual workers.

It is important to identify the chemicals of concern from that particular preservative, its natural concentrations and the potential adverse human health effects that may result from exposure. The severity of adverse health effects vary by dosage, duration and route of exposure (e.g. skin contact, ingestion, inhalation) and the sensitivity of the individual.

Several organizations provide resources that are available on workplace safety and chemical exposures at workplace:

• Provincial Agencies (see Appendix 1)
• Workplace Hazardous Materials Information System (WHMIS)
  • WHMIS - Labelling Requirements
• Health Canada
  • Environmental and Workplace Health
  • Water Quality
• Health Canada’s Pest Management Regulatory Agency (PMRA)
  • Consumer Product Safety
  • Pesticides and Pest Management
• Canadian Centre for Occupational Health and Safety (CCOHS)
• American Conference of Governmental Industrial Hygienists(ACGIH)
• Office of Pesticide Programs (United States Environmental Protection Agency)
• Occupational Safety & Health Administration (OSHA)
• Agency for Toxic Substances and Disease Registry (ATSDR)
• World Health Organization
• International Programme on Chemical Safety
• International Labour Organization, ICSC Card database
• National Research Council of Canada

Material safety data sheets (MSDS) and the pesticide label also contains information about potential health effects associated from the exposure and safety precautions about handling of a particular preservative.

Provincial occupational health and safety regulatory agencies have set Occupational Exposure Limits (OELs). These OELs differ from province to province but have a basis in the threshold limit values (TLVs) and biological exposure indices (BEIs) for chemical exposures in industrial settings. These limits and indices indicate exposure at or below the level which does not create an unreasonable risk of disease or injury. Provinces may have different values than the most current American Conference of Governmental Industrial Hygienists (ACGIH). Get informed with your local authorities.

According to the ACGIH

• TLVs® and BEIs® are determinations made by a voluntary body of independent knowledgeable individuals. They represent the opinion of the scientific community that has reviewed the data described in the documentation, that exposure at or below the level of the TLV® or BEI® does not create an unreasonable risk of disease or injury.
• TLVs® and BEIs® are not standards. They are guidelines designed for use by industrial hygienists in making decisions regarding safe levels of exposure to various chemical substances and physical agents found in the workplace. In using these guidelines, industrial hygienists are cautioned that the TLVs® and BEIs® are only one of multiple factors to be considered in evaluating specific workplace situations and conditions. (5)

Simplified definitions that will be useful for establishing workplace exposure monitoring programs include:

1. Threshold limit value - Time weighted average (TLV-TWA): the TWA concentration for a conventional 8hr/workday, 40hr/week work schedule
2. Threshold limit value - Short-term exposure limit (TLV-STEL): spot exposure for a duration of 15 minutes, that cannot be repeated more than 4 times per day
3. Threshold limit value - Ceiling limit (TLV-C): absolute exposure limit that should not be exceeded at any time

Some individuals could be more sensitive to the exposure of certain chemicals and wood preservatives. Regular medical surveillance of workers that are exposed to certain preservatives and hazardous chemicals should be required. Section 6.4 provides additional recommendations on the biological monitoring of exposed workers.

Prior to employment, workers should be notified of the potential risks and effects of preservatives. A pre-employment check-up that is specifically designed by an occupational physician to verify that they are not medically sensitive to any of the chemicals used at the facility should be conducted. The information should not be used to bar workers from employment but to ensure that proper precautions are applied.

Table 4 and Table 4.1 are templates that provides an example of a summary table on potential health effects of exposure to the preservative solutions.

4.1 Special Sensitivity

Natural sensitivity to the toxic effects of pesticide exposure varies. Some workers may be especially sensitive, including individuals with pre-existing skin problems, a history of liver or kidney disease, or a history of metabolic disorders caused by conditions such as diabetes or thyroid disease (6, 7). Prior to employment, workers should be informed of any potential effects and potential particular sensitivities. The information should not be used to bar workers from employment but to ensure that proper precautions are applied.