The risks posed by a substance are determined by both its hazardous properties (potential to cause adverse human health or ecological effects) and the amount or extent to which people or the environment are exposed.
When needed, the Government applies risk management instruments under CEPA and other federal acts to help prevent or reduce potential harm.
The first draft assessment for boric acid, its salts, and its precursors was originally published in July 2016. Since then, new use and exposure information, including additional environmental monitoring and human biomonitoring data from the Canadian Health Measures Survey (CHMS), became available. As a result, the draft assessment was updated.
The Government is still proposing that boric acid, its salts and its precursors are harmful to human health and the environment at levels of exposure considered in the assessment.
Boric acid may pose a risk to human health from exposure to a variety of products available to consumers, including some arts and crafts materials and toys, self-care products (such as cosmetics, natural health products and non-prescription drugs), flame retardant use in mattresses and futons, and do-it-yourself (DIY) products, among others. Boric acid is associated with adverse health effects (reproductive and developmental effects).
These substances may also pose a risk to aquatic environments through releases to water from one facility that processed recovered slags (by-product of the metallurgical smelting process) for precious and other base metals.
Risk management actions are proposed to help reduce exposures of people in Canada and the environment to these substances.
The assessment focuses on boric acid, a common moiety of concern. For the assessment, the moiety refers to the part of a molecule that is expected to have toxicological significance. The assessment therefore considers boric acid, its salts and its precursors, including any boron-containing substance that may release boric acid.
Boron is a naturally occurring element in the earth's crust. It is not found naturally in its elemental form, but rather found in the form of borosilicate minerals, boric acid, or borates.
Naturally occurring sources for boric acid include sea-salt aerosols, soil dusts, volcanoes, burning biomass (for example, forest fires), plant aerosols, and rock and soil weathering. Human-made sources can include the manufacture, import and use of boric acid, its salts and its precursors in products and manufactured items.
According to information gathered by the Government, these substances are used in a wide variety of products in Canada, including cellulose and fibreglass insulation manufacturing, industrial and consumer cleaning products, self-care products (that is, cosmetics, natural health products, and non-prescription drugs), other chemicals, gypsum board manufacturing, engineered wood products manufacturing, oil and gas extraction, agriculture (for example fertilizers), pulp and paper manufacturing and packaging, rubber manufacturing, chemical manufacturing, metallurgical applications, and surface finishing.
In addition, boric acid, its salts and its precursors are present in a number of products available to consumers including arts and crafts materials and toys, DIY products (including adhesives and sealants, automotive maintenance, home maintenance, paints and coatings), flame retardants, and swimming pool and spa maintenance products.
Other sources of boric acid include the incidental production and later release of boric acid from activities such as coal-fired power generation, metal ore mining, base metals and precious metals smelting and refining, coal mining, oil sands extraction and processing, oil and gas extraction, pulp and paper manufacturing, wastewater treatment (including the land application of biosolids), and waste disposal (landfill leachate).
Human and ecological exposures
People in Canada are mainly exposed to boric acid from its natural and human-made presence in the environment (for example, in drinking water and air) and food. Boron is an essential micronutrient for plant growth. Naturally occurring boron in fruits, vegetables and drinking water are the primary contributors to background exposure. Dietary exposure from natural sources is not considered to be a concern for people in Canada.
The assessment indicates that people in Canada are exposed to boric acid from a variety of uses and products. There are many uses and products that contribute to exposure at levels that are similar to or well above background exposure from food and environmental sources.
Human biomonitoring is the measurement of substances in blood, urine or other human tissues and fluids (such as human milk, nails or hair) through health studies or surveys, such as the CHMS. The information on measured levels in humans is important for estimating exposure to people in Canada.
Exposure to boron was characterized using urine biomonitoring data from the CHMS and the First Nations Youth, Environment and Health study, and blood biomonitoring data from the Alberta Biomonitoring Program, the Northern Saskatchewan Prenatal Biomonitoring study, and several smaller studies conducted in Europe.
Total boron measured in urine and blood provides a measure of exposure that may occur from all routes. This includes oral (by mouth), dermal (skin), and inhalation (breathing in) exposures and all sources, such as environmental sources, food, and frequently or commonly used products.
Ecological exposure scenarios were developed for various activities that represent significant sources of release of boric acid, its salts and its precursors to the environment. These scenarios included pulp and paper manufacturing, releases from products available to consumers, rubber manufacturing, electroplating, fiberglass insulation manufacturing, cellulose insulation manufacturing, gypsum board manufacturing, engineered wood manufacturing and fertilizer manufacturing.
Exposure scenarios were also developed for the following sectors, based on their potential to release boric acid incidentally (as a by-product): coal-fired power generation, metal ore mining, base and precious metals smelting and refining, coal mining, oil sands extraction and processing, and wastewater and waste management.
Boric acid has been classified internationally by ECHA as a reproductive toxicant according to the harmonized classification and labelling approved by the European Union. It has also been identified in the European Union as a substance of very high concern because of its suspected reproductive and developmental effects.
Acute (can occur rapidly following short-term exposure) and chronic (caused by repeated, low-dose exposure) critical effects identified for characterizing the risk to human health for boric acid were developmental effects (skeletal abnormalities) and reproductive effects (decreased testicular weight), respectively.
In addition, effects following inhalation exposure to boron trifluoride were identified, and were used to characterize risk to boron trifluoride monoetherate.
Ecological effects in the assessment focused on the effects of boric acid in aquatic and soil-dwelling organisms.
A metalloid ion like boric acid is considered infinitely persistent because it cannot break down any further, though it can transform into different chemical species or partition among different phases within an environmental medium.
Boron, absorbed as boric acid, does not have the potential to accumulate (build up) in most aquatic organisms, although it has been observed to accumulate in some aquatic plants and algae. Evidence suggests that boric acid does not biomagnify (increase in concentration as it is passed up the food chain) in the environment.
Consideration of subpopulations who may have greater susceptibility or greater exposure
There are groups of individuals within the Canadian population who, due to greater susceptibility or greater exposure, may be more vulnerable to experiencing adverse health effects from exposure to substances.
Certain subpopulations are routinely considered throughout the assessment process, such as infants, children, and people of reproductive age. For instance, age-specific exposures are routinely estimated, and developmental and reproductive toxicity studies are evaluated for potential adverse health effects.
For boric acid, its salts and its precursors, Canadian human biomonitoring data in children, pregnant people, and certain Indigenous communities were used to inform consideration of these populations and taken into account in the risk assessment outcomes. Children have the highest exposure to boric acid and males or people assigned male at birth of all ages are more susceptible to adverse health effects of boric acid than pregnant women and pregnant people, the developing fetus, and children. In addition, socio-demographic, behavioural and physical factors associated with exposure were considered.
Risk assessment outcomes
Assessments focus on information critical to determining whether substances are harmful to human health or the environment under CEPA. This is done by considering scientific information, including information, if available, on subpopulations who may have greater susceptibility or greater exposure, vulnerable environments and cumulative effects and by incorporating a weight of evidence approach and precaution. The potential for cumulative effects was considered in the assessment by examining cumulative exposures to the moiety of boric acid.
Based upon a comparison of total levels of boric acid measured in urine, and levels associated with health effects (decreased testicular weight), it was determined that there may be a risk to human health from boric acid, its salts and its precursors.
It was determined that boric acid, its salts and its precursors may cause a risk to human health from the use of some arts and crafts materials and toys, cleaning products, flame retardants, DIY products, self-care products (such as cosmetics, natural health products and non-prescription drugs), and swimming pool and spa maintenance products. This was based upon the comparison of levels to which people in Canada may be exposed to these substances and levels associated with health effects of concern.
For the ecological assessment, risk quotient analyses were performed to compare estimated concentrations of boric acid in the environment to concentrations that may cause adverse effects. For most sectors and activities that release boric acid, the potential ecological harm is low. However, potential ecological concern was identified for aquatic releases of boric acid from one facility that processed recovered slags (by-product of the metallurgical smelting process) for precious and other base metals from the metal ore mining section.
Proposed assessment conclusions
The Government is proposing that boric acid, its salts and its precursors are harmful to human health at levels of exposure considered in the assessment.
The Government is also proposing that boric acid, its salts and its precursors are entering or may enter the environment at concentrations that are harmful.
Boric acid, its salts and its precursors are proposed to meet the persistence criteria but not the bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations of CEPA.
Preventive actions and risk reduction
If the proposed conclusion is confirmed in the final assessment, the Government will consider adding boric acid, its salts and its precursors to Part 2 of Schedule 1 to CEPA. Adding a substance to Schedule 1 does not restrict its use, manufacture or import. Rather, it enables the Government to take enforceable risk management actions under CEPA.
Toxic substances that pose the highest risk (that is, meet certain criteria) are added to Part 1 of Schedule 1. These are prioritized for total, partial or conditional prohibition.
Other toxic substances are added to Part 2 of Schedule 1 and are prioritized for pollution prevention actions, which may include prohibition.
Regulations specifying criteria for the classification of substances that pose the highest risk or that are carcinogenic, mutagenic or toxic to reproduction will be developed. When criteria are available, some substances considered for addition to Part 2 of Schedule 1 may instead be considered for addition to Part 1 of Schedule 1.
Publication of the risk management scope aims to inform interested parties of proposed risk management options and initiate discussions about their development. The Government will consider the following actions to address human health and ecological concerns:
Flame retardant uses: For mattresses and futons containing boric acid used as a flame retardant, regulatory measures to reduce or eliminate exposure;
Cleaning products: Regulatory or non-regulatory actions to help reduce human exposure to cleaning products containing boron, including consumer products used as an abrasive powder, general purpose powder cleaner, carpet spot remover powder, floor cleaning powder and laundry powder;
Swimming pool and spa maintenance products: Regulatory or non-regulatory actions to help reduce exposure to boric acid during swimming activities (excluding those uses regulated under the Pest Control Products Act, such as algaecides and sanitizer pool products containing boron as a formulant);
DIY products: Regulatory or non-regulatory actions to help reduce exposure to boric acid from certain DIY products available to consumers, and in particular airless spray paints for rust, that contain boron;
Arts and crafts materials and toys: For home-made clays, slimes, and crystals, prepared with boric acid and intended for children's use, an updated public information document outlining the potential health risks associated with boric acid and home-use of borax (as boric acid) to discourage consumers from this practice;
Cosmetics: Modify the existing entry for "Boric acid and its salts" on Health Canada's Cosmetic Ingredient Hotlist to help reduce exposure to boric acid, its salts and its precursors from certain products applied to or in contact with the skin (for example body creams, hair colours and massage oils). The Hotlist is used to communicate that certain substances may not comply with requirements of the Food and Drugs Act or the Cosmetic Regulations. Under Canadian legislation, cosmetics that contain substances that are harmful to the user cannot be sold;
Natural health products and non-prescription drugs: Modifying the existing entries for boric acid, its salts and its precursors in Health Canada's Natural Health Products Ingredients Database to help reduce exposure to boric acid, its salts and its precursors from certain natural health products and non-prescription drugs. Actions may aim to lower the concentration of these substances when used in certain natural health products or non-prescription drugs to levels that are protective of human health. In addition, reviewing the maximum daily dose allowed and associated conditions of use for boron under the Natural and Non-prescription Health Products Directorate's Multi-Vitamin/Mineral Supplements and Multiple Ingredient Joint Health Products monographs; and
For ecological risk from a metal ore processing mill: Working with provincial authorities and a specific mill to identify additional facility-specific risk management actions under provincial or federal jurisdiction. Further risk management actions for other facilities in the metal ore mining sector are not currently under consideration.
Information is being sought by the Government to inform risk management decision-making. Details can be found in the risk management scope, including where to send information during the public comment period, ending May 7, 2025.
Risk management actions may evolve through consideration of assessments and risk management actions published for other substances. This is to ensure effective, coordinated, and consistent risk management decision-making.
Use the Substances Search tool to find substances that are referenced in certain legislative or regulatory instruments or on Government of Canada websites.
Related resources
Substances in this group are found in products available to consumers. People in Canada should follow any safety warnings and directions related to the product and dispose of products responsibly.
In addition, these substances may be found in arts and crafts materials for children. Health Canada has provided general information on using arts and crafts materials safely.
Boron has been assessed by the Federal-Provincial-Territorial Committee on Drinking Water, and a guideline technical document has been published by Health Canada.
Assessments conducted under CEPA focus on risks of exposure of the general population, including populations who may be disproportionately impacted. Hazards related to chemicals used in the workplace are defined within the Workplace Hazardous Materials Information System (WHMIS). The Government of Canada recognizes that it is the responsibility of the federal, provincial and territorial occupational health and safety organizations to coordinate legislation for the safe use of chemicals in the workplace. We are working to support this role by integrating the information, tools, and technical expertise of the CMP and Health Canada's Workplace Hazardous Products Program.
