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 the Hazardous Substances Data Bank (HSDB) for more information.[4,5]
In 1987, elemental lead and inorganic lead compounds were classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans. 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 reclassified inorganic lead compounds, upgrading their classification to Group 2A, probably carcinogenic to humans. Organic lead compounds remains in Group 3, and elemental lead remains in Group 2B.
Despite the acknowledged difficulty in controlling for confounding variables, IARC's decision to reclassify inorganic lead compounds was based on consistently observed increases in several cancers, including lung, stomach, kidney, brain, and nervous system cancer. Some of these epidemiologic studies were based on small numbers. There was also 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 are well documented. They include effects on the neurological, cardiovascular, and hematological systems. Reproductive effects, including miscarriage and preterm 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 having a large number of studies examining outcomes in children. The developing nervous systems of children are particularly sensitive to lead and even small amounts can be hazardous prenatally and in young children.
The primary use of lead is in lead-acid batteries for automobiles and other vehicles (80% of total use).[16,17] Over the past five years, lead-acid storage batteries constituted 75% 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. Other battery applications include stationary batteries used for backup power.
Lead oxide, or red lead, is the primary paint primer for iron and steel.
Because it is highly dense, lead is suitable for shielding radiation. It is used for this purpose in television, video, and computer screens, as well as in storage containers for nuclear waste and in x-ray shielding aprons.
Lead is also used in: roof sheeting, mostly in Europe; chemical compounds and alloys; and manufacture of cable sheathing, circuit boards, lead shot and ammunition, dyes, varnishes and resins, pigments, automotive parts, explosives, paper coatings, ceramics, and rubber and plastics.[17,18]
Canadian Production and Trade
In 2009, Canada was the 8th leading world producer and supplier of lead. It has since declined, owing to the 2013 closure of the country's largest lead mine in New Brunswick.
Lead has been mined in every Canadian province but Alberta, Saskatchewan, and Prince Edward Island. The Sullivan mine, which operated in Kimberley, BC for nearly 100 years, closed in 2001. Two Canadian mines produced lead in concentrate form in 2015: Nyrstar NV's Myra Falls mine in British Columbia, and Trevali Mining Corporation's Caribou mine in New Brunswick.
Canada operates two primary lead and four recycled lead smelters. The latter smelters recycle significant amounts of used lead-acid batteries; recycled lead production comprised 53% of Canada's total refined lead metal production in 2015.
Production and Trade
2,762 t of 'lead ores and concentrates'
662 t of 'lead oxides; red lead and orange lead'
259,333 t of 'unwrought lead'
115,866 t of 'lead ores and concentrates'
6,418 t of 'lead oxides; red lead and orange lead'
2,313 t of 'unwrought lead'
t = tonne
Inhalation is the most common route of occupational exposure, followed by ingestion.
CAREX Canada estimates that approximately 277,000 Canadians are exposed to lead in their workplaces. The largest industrial groups exposed include public administration (e.g. police officers), followed by building equipment contractors, and automotive repair and maintenance. In terms of occupation, the two largest exposed groups are welders, followed by police officers. Other large occupational groups that are at higher risk to lead exposure include auto mechanics, plumbers, and pipefitters.
Additional occupations that are 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, and firing ranges.
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. CAREX Canada's environmental estimates indicate that lead concentrations in indoor air do not result in an increased risk of cancer (low data quality). However, CAREX Canada estimates that lead concentrations in indoor dust result in an increased risk of cancer (moderate data quality).
Food has been a primary contributor of lead exposure in the past. However, since lead solder is no longer used in cans, current levels of exposure through ingesting food are generally low. Lead can enter food grown in contaminated soils, stored in containers with lead-based glazes or in leaded crystal. CAREX Canada estimates that lead concentrations in food or beverages do not result in increased risk of cancer (low data quality).
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. 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 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. CAREX Canada estimates that lead concentrations in outdoor air do not result in an increased risk of cancer (moderate data quality).
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. CAREX Canada estimates that lead concentrations in drinking water do not result in an increased risk of cancer (moderate data quality).
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 second cycle of the survey was completed in 2011 and a second report on human biomonitoring of environmental chemicals was released in April 2013.
The biomonitoring data from the second cycle of the CHMS, which included 6,400 Canadians, found the geometric mean blood concentration for lead to be 1.2 µg/dL. This level is approximately 0.1 µg/dL lower than the average blood lead levels found during the first cycle of the CHMS (completed in 2009) and substantially lower than in 1978, when the national levels were last measured prior to the CHMS. In the third cycle of the CHMS in 2012-2013, the geometric mean was 1.1 µg/L, which was again 0.1 µg/L lower than the previous measurement. Smokers were found to have significantly higher levels of lead in their blood than non-smokers.
In 1978, approximately 27% of Canadians had a blood lead level (BLL) at or above the current recommended intervention level of 10 µg/dL. Today, almost all Canadians have a BLL below the current intervention level. However, recent scientific studies have provided sufficient evidence to suggest that BLLs below 5 µg/dL are associated with adverse health effects. The blood level intervention level is currently under review.
Searches of Environment Canada's National Pollutant Release Inventory (NPRI) and the US Household Products Database yielded the following results on current potential for exposure to lead in Canada:
NPRI and US Household Products Database
Substance name: 'Lead (and its compounds)'
Released into Environment
Foundries, defense services, non-ferrous metal production and processing, metal ore mining, iron and steel mining (611 facilities)
Sent to off-site recycling
US Household Products 2016
Results: 14 products
Solder kits (8), motor oils (4), glazes (1), and pet care (1)
'lead compounds, unspecified'
t = tonne
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. Click here to learn more about policies specific to lead in the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at email@example.com.