Selenium and its compounds – information sheet

Updated May 12, 2021:

The Final Screening Assessment for Selenium and its compounds was published on December 16, 2017 under the Substance Groupings Initiative of the Chemicals Management Plan (CMP). The assessment is summarized in this information sheet. The section below entitled "Preventive actions and reducing risk" communicates updates in risk management activities, namely:

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  • The Government of Canada conducted a science-based screening assessment, under CEPA 1999, to address the potential for harm to Canadians and to the environment from selenium and its compounds.
  • The risk posed by a substance is determined by considering both its hazardous properties (its potential to cause adverse human health or ecological effects) and the amount of exposure there is to people or to the environment.
  • As a result of the screening assessment, selenium and its compounds are considered harmful for certain subpopulations in Canada that have higher selenium intake; however, they are not considered harmful to the general population of Canada. Selenium is an essential nutrient for human health. Selenium and its compounds were also concluded to be harmful to the environment.

About these substances

  • The screening assessment focused on the selenium moiety, and therefore includes all forms of selenium found in commerce and those found in the environment, which are referred to collectively as selenium and its compounds.
  • The assessment focused on the potential for harm from elevated selenium exposure. These substances were assessed as the Selenium-containing Substance Grouping as part of the Substance Groupings Initiative of the Chemicals Management Plan (CMP).
  • Selenium is a naturally occurring element in the environment and can be found in minerals such as pyrite, chalcopyrite, pyrrothite, and sphalerite. Selenium is also found in crude oil and coal deposits.
  • Although there are no mines for selenium in Canada, it can be recovered from the processing of other material.
  • Selenium is an essential nutrient for human health and for many organisms in the environment.
  • A certain amount of selenium is needed to perform important functions in the body. Selenium plays a role in reproductive, neurological, and immune functions with an estimated average daily requirement of 45 µg/day; however, there are potential risks to certain subpopulations that have elevated selenium exposure levels. The Tolerable Upper Intake Level (UL) for selenium has been identified as 400 µg/day and represents total intake from food, water and supplements. The UL is the highest average daily nutrient intake level likely to pose no risk of adverse health effects to almost all individuals. It is not a recommended intake level.
  • The assessment considered the combined exposure to all selenium compounds from natural or industrial sources, whether it is present in water, sediment, soil, air, food, or products available to consumers.
  • According to the assessment, selenium-containing substances are found in natural health products (for example, multi-vitamin/mineral supplements and anti-dandruff shampoos). It may also be used as a component in pigments (in plastics, paints, ceramics and glass), rubber manufacture, agriculture (soil supplements, animal feed, and pesticides), electronic and electrical equipment, medicines, cosmetic products, consumer products, lubricants, and metallurgical applications.
  • Under the Food and Drug Regulations, selenium cannot be added to food, except for infant formula, formulated liquid diets, in food represented for use in a very low energy diet or in meal replacements and nutritional supplements. Minimum and maximum amounts of selenium which can be added are specified for these types of foods as described in those regulations. Some other foods may also be supplemented with selenium but only after a review by Health Canada and provided that compositions and labeling requirements are met.

Human and ecological exposures

  • All Canadians are exposed to selenium through their diet. Cereals, breads, baked goods, grains, and flours are the main sources of selenium exposure for the general population.
  • Use of multi-vitamin/mineral supplements providing more than 200 µg/day of selenium can result in elevated intake.
  • Some Inuit living in various communities in Arctic Canada have been identified as a sub-population with elevated blood selenium levels, likely due to the consumption of certain selenium-rich traditional foods (such as marine mammals). Subsistence fishers, including First Nations people, consuming fish with elevated selenium levels (for example, around some mining operations) are another sub-population identified as potentially being exposed to elevated levels of selenium.
  • The assessment of selenium and its compounds was based on the results of human biomonitoring studies. The information on measured levels in humans is important in estimating exposure to Canadians.
  • Natural sources of selenium include volcanic activity, sea salt spray, wildfires, weathering of selenium-rich soils and rocks. Selenium also enters the air from rivers and lakes.
  • Industrial processes and products are also a significant source of selenium. These include selenium production, the manufacture, import and uses of selenium-containing substances, as well as products and manufactured items. These also include the release of selenium as a result of activities such as fossil fuel combustion, mining, base metal smelting and refining operations, agricultural activities, and wastewater treatment.
  • Once released into the environment, selenium may enter the air, water, and soil, and will eventually make its way into sediments and organisms such as fish.

Key health and ecological effects (hazard)

  • Selenosis was considered to be the important or critical health effect for selenium, and it has been observed in humans as a result of elevated exposure to selenium. This is characterized by symptoms such as hair loss, nail loss and deformities, garlic odour in breath, weakness, decreased cognitive function, and gastrointestinal disorders.
  • Selenosis is the basis for many international regulatory reference values, including the UL of 400 µg/day established by the Institute of Medicine (IOM; now called the National Academy of Medicine) for populations in Canada and the United States.
  • Using a biomonitoring approach, total selenium concentrations in whole blood found in some sub-populations exceed this UL and exceeds concentrations at which selenosis has been observed in humans.
  • In addition, guidance values developed to protect human health and based on the IOM UL of 400 mg/day, were used to characterize the risk for subsistence fishers (high fish consumption) and individuals taking multi-vitamin/mineral supplements providing higher levels of selenium (for example, above 200 µg/day).
  • Reproductive failure in egg-laying vertebrates (such as fish, waterbirds, and amphibians) from long-term exposure to elevated levels of selenium is the most severe ecological effect. In fish, excess levels of selenium may accumulate in fish eggs and affect developing embryos and larvae.
  • In birds, reduced egg hatchability and increased embryonic deformities were the main ecological effects of selenium.

Risk assessment outcomes

  • The screening assessment focused on potential harm from elevated levels of selenium and does not provide a review of the health benefits from a nutritional perspective.
  • There are 3 sub-populations in Canada with exposures to selenium which exceed the UL (that is, exposures are higher than the tolerable upper intake level):
    • Total selenium in whole blood found in some Inuit populations exceed the whole blood equivalent of the UL, and exceeds concentrations at which selenosis has been observed in humans.
    • In addition, there are exceedances of a guidance value for high fish consumption (subsistence fishers including First Nations people) around "point" (local) sources of selenium such as mines, smelting and refining facilities.
    • Lastly, there are potential exceedances of the UL for individuals taking multi-vitamin/mineral supplements with higher levels of selenium.
  • Results of the final screening assessment indicate that selenium and its compounds may remain in the environment for a long time, accumulate in, and cause harm to organisms.
  • The Government of Canada published the Final Screening Assessment for Selenium and its Compounds on December 16, 2017.

Screening assessment conclusions

  • The Government concluded that selenium and its compounds are harmful to human health, based on potential for elevated levels in certain subpopulations in Canada. Selenium and its compounds are not expected to be harmful to the general population of Canada.
  • The Government also concluded that selenium and its compounds are entering the environment at levels that are harmful to the environment.
  • The selenium moiety has been determined to meet the persistence and bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations of CEPA 1999. However, selenium is a naturally occurring element, with both natural and anthropogenic sources.

Preventive actions and reducing risk

  • The Government of Canada published the proposed Risk Management Approach Document for Selenium and its Compounds on December 16, 2017. This publication had a 60-day public comment period that ended on February 14, 2018.
  • On May 12, 2021, Selenium and its compounds were added to Schedule 1 of CEPA 1999, also called the List of Toxic Substances. Adding a substance to the list does not restrict its use, manufacture or import. Rather, it enables the Government to take risk management actions under CEPA 1999.
  • The Government is taking action to reduce releases of selenium in the following sectors to address ecological concerns:
    • Coal mining: by developing a regulatory approach to limit selenium discharges;
    • Metal mining: by enhancing information gathering under the Metal and Diamond Mining Effluent Regulations (MDMER) to determine if additional risk management is required;
    • Base metals smelting and refining: by addressing facilities that combine their effluent with mining operations through the action proposed for the metal mining sector, and by working with industry to gather additional information through a voluntary initiative with the facilities that are not subject to the MDMER;
    • Power generation: by implementing the performance standards of the Reduction of Carbon Dioxide Emissions from Coal-Fired Generation of Electricity Regulations that came into force in July 2015 and are expected to reduce the potential for risk from release of metals, including selenium, as a co-benefit;
    • Agriculture: by continuing to collaborate with other government departments and industry on appropriate science initiatives, as required; and
    • Publicly owned wastewater treatment: by examining the effect of the Wastewater Systems Effluent Regulations on selenium to determine if additional risk management is required upstream.
  • The Government is also taking action in the following areas to address human health concerns:
    • Natural health products: The Government lowered the maximum daily dose of selenium from 400 mg/day to 200 mg/day. Canadians are reminded to only take multi-vitamins/mineral supplements that have a Natural Product Number (NPN) on the label. Ingredient information can be found on the product label.
    • Food consumption advice for specific sub-populations: Upon request from relevant public health authorities (such as provinces or territories), Health Canada will provide health risk assessments and opinions on the potential risks posed by chemical substances in traditional foods or in the interpretation of biomonitoring results. Any subsequent risk management advice developed from these assessments, such as issuing a consumption advisory, would be the responsibility of the relevant authority.
    • Research and monitoring: The Government is continuing to carry out research and monitoring on selenium. For instance, the Government will continue to monitor the exposures of the general population to selenium through the Canadian Health Measures Survey. Selenium is also identified as a contaminant of concern in the Northern Contaminants Program Human Health Blueprint.
  • Further information and updates on risk management actions for substances managed under the CMP can be found in the risk management actions table and the two year rolling risk management activities and consultations schedule.

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