Lindane Environmental Exposures
Lindane Environmental Exposures
Lindane does not occur naturally. Although it does biodegrade, the process is slow and therefore lindane persists after being introduced to the environment through human activities. Lindane may be found in air, soil, sediments, and water. It generally has low solubility in water, is volatile from soil and water, has low potential mobility in soil due to high adsorption, and has the potential to bioaccumulate.
The general public may be exposed to lindane through dermal absorption, ingesting contaminated foods, breathing contaminated air, or being in contact with contaminated soil or water. Lindane is metabolized into many other substances, including chlorophenols, some of which have toxic properties.
Volatilization from soil is the most important route of dissipation for lindane. As a vapour in the air it attaches to dust particles, on which it can persist and travel long distances depending on the season and weather conditions.[1,3] Another major source of lindane in the air is fugitive dust particles released as wind erodes contaminated soil. Contaminated particles are gradually broken down and removed by rain or other compounds found in the atmosphere.
Persistent organic pollutants (POPs) including lindane were found at high concentrations in the Arctic in the 1980s. Lindane was transported to these regions through atmospheric deposition and ocean currents. Fortunately, levels of lindane in the food web and air have since decreased; this trend accelerated in 2002, coinciding with increased restrictions on lindane in Canada.
Dermal absorption is an important route of exposure given that lindane was formerly used to treat lice and other parasites. Dermal absorption typically varies between 10-35%, although some studies measured absorption values as low as 9% and up to 100%. Absorption depends on the pesticide formulation and skin characteristics of the person exposed. There is a 20-fold variation in absorption reported for children due to an increased surface area to volume ratio.[1,2]
Lindane bioaccumulates in the fat tissues of organisms. Foods with the greatest potential to contain and transfer lindane therefore include milk, eggs, other dairy products, and some seafood. Pickles and raw mushrooms may also contain high concentrations of lindane. Exposure can occur via lindane residues on food products or accumulation in animal tissue. Lindane has also been found in breast milk.
Northern Aboriginal peoples are more likely to experience potential health effects resulting from lindane bioaccumulating in traditional foods. The majority of Aboriginal households (90%) in the Northwest Territories report consuming traditional foods such as harvested wildlife and or marine mammals.
CAREX Canada estimates that less than one extra cancer per million individuals occurs due to exposures through diet (including drinking water and foods and beverages), indicating that exposure through this route does not result in an increased risk of cancer (very low data quality).
CAREX Canada also estimates that lindane levels in outdoor air (moderate data quality) and indoor dust (low data quality) do not result in an increased risk of cancer. However, we estimate that lindane concentrations in indoor air do result in an increased risk of cancer (very low data quality).
Cancer Risk Estimates
Potential lifetime excess cancer risk (LECR) is an indicator of Canadians’ exposure to known or suspected carcinogens in the environment. When potential LECR is more than 1 per million in a single pathway, a more detailed risk assessment may be useful for confirming the need to reduce individual exposure. If measured levels of lindane in relevant exposure pathways (outdoor air, indoor air, indoor dust, drinking water, and food and beverages) decrease, the risk will also decrease.
Potential LECR is calculated by multiplying lifetime average daily intake (the amount inhaled or ingested) by a cancer potency factor or unit risk factor. More than one cancer potency factor may be available, because agencies interpret the underlying health studies differently, or use a more precautionary approach. Our results use cancer potency factors from Health Canada, the US Environmental Protection Agency (US EPA), and/or the California Office of Environmental Health Hazard Assessment (OEHHA).
The calculated lifetime daily intake and LECR results for lindane are provided in the tables below. For more information on supporting data and sources, click on the Methods and Data tab below.
Calculated Lifetime Daily Intake
Lifetime Excess Cancer Risk (per million people)
*LECR based on average intake x cancer potency factor from each agency
Potential LECR assumes exposure occurs at the same level, 24 hours per day, for 70 years. This is rarely true for any single individual, but using a standard set of assumptions allows us to provide a relative ranking for known and suspected carcinogens across different exposure routes. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
Methods and Data
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As a national organization, our work extends across borders into many Indigenous lands throughout Canada. We gratefully acknowledge that our host institution, the University of British Columbia Point Grey campus, is located on the traditional, ancestral and unceded territories of the xʷməθkʷəy̓əm (Musqueam) people.