Elemental lead is a soft, highly malleable and ductile metal that is insoluble in water. Lead rarely exists naturally in its pure form. It is typically found in low concentrations in the earth’s crust as the mineral galena (lead sulfide). Lead forms both inorganic and organic compounds with many substances, including acetate, arsenic, antimony, chlorine, oxygen, and phosphate. There are numerous synonyms and product names for lead; see IARC and HSDB for more information.[4,5]
In 1987, elemental lead and inorganic lead compounds were classified by IARC in 1987 as Group 2B, possibly carcinogenic to humans, while organic lead compounds were classified as Group 3, not classifiable as to their carcinogenicity to humans. In 2006, IARC re-examined the evidence regarding the carcinogenicity of inorganic and organic lead compounds. Based on new evidence reviewed, IARC re-classified inorganic lead compounds, upgrading their classification to group 2A, probably carcinogenic to humans. Organic lead compounds remained Group 3.
Despite the acknowledged difficulty in controlling for confounding variables, IARC’s decision to reclassify inorganic lead compounds was based on consistently observed increases in lung and stomach cancers in epidemiological studies of inorganic lead compounds; observed cancers of the kidney, brain and nervous system (although studies were based on small numbers); animal data suggesting a causal relationship between inorganic lead exposure and renal cancer; and fairly strong animal data for brain cancer.
Other health impacts of lead exposure have been studied at length, with well documented effects on the neurological, cardiovascular and hematological systems. Reproductive effects, including miscarriage and pre-term delivery in women, and decreased fertility in men are also associated with moderately high levels of lead exposure.
The effect of lead is the same regardless of whether exposure occurs through inhalation or ingestion. The lead literature is unique in the number of studies examining outcomes in children. Their developing nervous systems are particularly sensitive to lead and even small amounts can be hazardous prenatally and in young children.
The most common use of lead (globally and in Canada) is lead-acid storage batteries.[13,14] Over the past five years, lead-acid storage batteries constituted 80% of global lead consumption. Lead-acid storage batteries are produced for vehicles, emergency systems (hospitals), and for industrial batteries found in computers and fork lifts. Each car battery contains approximately 10 kg of lead.
Lead oxide, or red lead, is the primary paint primer for iron and steel.
Because its high density makes it suitable for shielding radiation, lead is used in television, video and computer screens, as well as in storage containers for nuclear waste and in x-ray shielding aprons.
Other uses include: stabilizers in plastic (PVC) piping, in decorative glass and in roof sheeting; consumer products such as a pigments and coatings (art materials); and rolled and extruded products, ammunition, alloys, and sheathing.
Canadian Production and Trade
In 2005, Canada was the 9th leading world producer and supplier of lead. In 2006, lead recycling (mostly from car batteries) accounts for 40% of total refined production in Canada.
Lead has been mined in every Canadian province but Prince Edward Island, Alberta, and Saskatchewan. The Sullivan mine operated in Kimberley BC for nearly 100 years, closing in 2001. Currently, the largest producing mine is the Brunswick Mine in NB. The only other operational mine in Canada is Myra Falls on Vancouver Island.
Canada's 5 metallurgical lead plants are located in Trail and Vancouver BC, Mississauga ON, Bathurst NB, and southern QC.
Production and Trade
82,393 t of lead in concentrate
250,464 t of refined metal production
Export: Solely to China
827 t of 'lead ores and concentrates'
Export: Mainly to US
936 t of 'lead oxides; red lead and orange lead'
Export: Mainly to US
261,935 t of 'unwrought lead'
Import: Mainly from US, Peru
59,601 t of 'lead ores and concentrates'
Import: Mainly from US
5,090 t of 'lead oxides; red lead and orange lead'
Import: Mainly from US
5,122 t of 'unwrought lead'
Inhalation is the most important route of occupational exposure, followed by ingestion.
The main occupations exposed include workers involved in mining, lead smelting and refining industries, battery production or recycling, steel welding or cutting operations, construction, rubber products and plastics industries, printing industries, firing ranges, radiator repair shops, and other industries requiring flame soldering of lead solder. Using lead in laboratories (mixing and weighing), lead based pigments and for leaded-glass are other potential exposures.
Environmental exposure to lead can occur through food, drinking water, air, soil, dust, and various consumer products. Ingestion of lead from dust, paint chips, and soil is of concern for young children in particular. The relative contribution to an individual’s exposure will depend on factors such as proximity to a point source, age of home and projects undertaken involving lead-based products.
Food has been a primary contributor in the past. Since lead solder is no longer used in cans, however, current levels of exposure through this route are generally low. Lead can enter food grown in contaminated soils, stored in containers with lead-based glazes or in leaded crystal.
Certain health care products, folk remedies, and toys—particularly imported toys—may contain lead.
Lead was phased out of paints in Canada, beginning in 1976. In 1995, the only Canadian producer of lead chromate, a yellow pigment, was Dominion Colour Corp. in Ontario. Some specialty coatings such as artists' paints may still contain lead, but all lead-containing products must be labeled. Renovation projects in older homes involving stripping or removing lead-containing paints, particularly when using heat, can result in significant exposures.
Most lead was removed from gasoline in the 1970s. Since then, levels in Canadian air have been generally lower, although smelters and refineries can be significant contributors to both outdoor air and soil levels.
Lead in drinking water in Canada is generally low. However, lead levels can be higher in older homes and ones with lead solder in the piping.
Waste disposal sites can also be point sources if lead-based products such as waste oil, coloured newsprint, battery casings or lead-painted wood are burned. Disposal of batteries, lead shot and fishing lures result in soil and groundwater contamination through leaching.
Lead is one of the substances selected for the Canadian Health Measures Survey (CHMS), a joint project of Statistics Canada and Health Canada to establish the current level of exposure to environmental contaminants. The first cycle, which includes a biomonitoring component, is being conducted from 2007-2009.
Preliminary biomonitoring data from the CHMS, released in November 2008 on approximately 2,500 Canadians, found a geometric mean blood concentration for lead of 1.37 µg/dL. This level is substantially lower than in 1978 when national levels were last measured. Less than 1% of those sampled exceeded Canadian guidelines of 10 µg/dL.
Searches of environmental and consumer product databases yielded the following results on current potential for exposure to lead in Canada:
NPRI and US Household Products Database
Search term: 'lead and its compounds'
Released into Environment
Mining, military, nickel refining, oil refineries, wastewater treatment, power generation, waste management, and pulp & paper industries (707 companies)