Bromodichloromethane
Full Profile
General Information
Bromodichloromethane (BDCM) is a colourless non-flammable liquid.[2] BDCM is one of a group of compounds called trihalomethanes (THMs) commonly found as by-products of the chlorination of drinking water. BDCM is formed when chlorine reacts with organic matter in the presence of bromine.[2] It is also naturally produced in small amounts by marine algae.[3]
Other trihalomethanes include chloroform, dibromochloromethane, and bromoform.[4] CAREX Canada is reviewing Canadian exposure to Chloroform as well as to Chlorination disinfection by-products as a group; please see the specific carcinogen profiles for more information.
Bromodichloromethane may also be referred to as dichlorobromomethane.[5] There are numerous other synonyms and product names; see HSDB for more information.[5]
Bromodichloromethane is classified by IARC as Group 2B, possibly carcinogenic to humans, based on data in experimental animals.[3] BDCM is an intestinal and kidney carcinogen in rats and mice.[3] The incidence of liver tumours was also elevated in female mice.[3]
Although several epidemiological studies suggest an association between chlorinated water containing BDCM and increased cancer rates, none have been able to control sufficiently for confounding variables such as other by-products of chlorination.[2]
There is some indication from animal studies that BDCM and other THMs containing bromine may be more toxic than those containing chlorine, but further study is needed to confirm additional health outcomes.[4] Exposure to high levels of BDCM have been linked to increases in adverse reproductive effects including spontaneous abortion or stillbirth, however evidence is insufficient to determine causality.[4] High doses of BDCM are also reported to result in central nervous system disturbances.[6]
Bromodichloromethane has been ranked by CAREX Canada as Group A (immediate high priority) for environmental settings and Group D (lowest priority) for occupational settings. Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure.
Regulations and Guidelines
No Occupational Exposure Limits (OELs) are available for BDCM.
Canadian Environmental Guidelines
| Jurisdiction | Limit | Year |
|---|---|---|
| Canadian Drinking Water Guidelines | 0.001 mg/L (MAC for all THMs) |
2006[7] |
Bromodichloromethane was not included in other Canadian government environmental guidelines reviewed.[8-10]
Canadian Agencies/Organizations
| Agency | Designation/Position | Year |
|---|---|---|
| Health Canada | NDSL* – Included | 2005[12] |
Bromodichloromethane was not included in other Canadian government chemical listings reviewed.[11,13]
Main Uses
BDCM is typically produced in small quantities and used primarily in the production of organic chemicals and as a reagent in laboratory research.[6] It has also been used to separate minerals and salts because of its solvent properties.[5]
Canadian Production and Trade
No data regarding production or trade of bromodichloromethane in Canada was identified.[15]
Occupational Exposures
BDCM is a low priority for occupational settings in CAREX Canada. Although there is potential for exposure to lifeguards and swim instructors who are exposed via working in or near swimming pools and hot tubs, BDCM will be assessed in a group with other related disinfection byproducts.[2]
Environmental Exposures
The most common exposure route for the general public is ingestion of chlorinated water.[6] Both dermal and inhalation are important routes of exposure when showering,[6] and particularly for those involved in competitive swimming.[16]
BDCM levels are usually higher in treated surface water than treated groundwater because there is more organic matter in surface water.[4] Concentrations of BDCM are also higher in summer months as warm temperatures contribute to increased organic matter and thus formation of disinfection by-products in surface water.[4]
Most water treatment plants across Canada are able to uphold the MAC (listed above) for BDCM in drinking water, with concentrations well below the national guidelines.[4] A few small community serving systems (providing water to < 4% of Canadians), however, have average levels above the Canadian guidelines. Smaller treatment systems have limited ability to remove organic matter before treating with chlorine, increasing the production of BDCM.[4]
Sources
- Wikimedia Commons Photo: Bromodichloromethane
- NTP 12th report on carcinogens for bromodichloromethane (2011)
- IARC monograph summary, Volume 71 (1999) (PDF)
- Health Canada Environmental and Workplace Health. Water Quality document for Trihalomethanes (2006)
- Hazardous Substances Data Bank (Search term: 'bromodichloromethane')
- ATSDR Toxicological Profile for bromodichloromethane (1989) (PDF)
- Canadian Drinking Water Guidelines (2010)
- Exposure Guidelines for Residential Indoor Air Quality (1987) (PDF)
- Health Canada (2010) Cosmetic Ingredient Hotlist
- Health Canada (2006) Food Additives Permitted for Use in Canada
- Health Canada’s Prioritization of the DSL (2006)
- Environment Canada: The Substances List (Search term: '75-27-4')
- CEPA List of Toxic Substances (1999)
- Environment Canada: Guidelines for the Notification and Testing of New Substances: Chemicals & Polymers (section 2.2)
- TradeMap (Free subscription required)
- Lindstrom, AB et al. (1997) Alveolar breath sampling and analysis to assess trihalomethane exposures during competitive swimming training. Environ. Health Persp., 105 (6), 636-642 (PDF)
Other Resources
- ASTDR ToxFAQ Sheet for bromodichloromethane (PDF)
- International Programme on Chemical Safety: Environmental Health Criteria 216. Disinfectants and Disinfectant By-Products
- IARC monograph, Volume 52 (1991): Chlorinated Drinking Water (PDF)
- Health Canada fact sheet: It's Your Health: Drinking Water Chlorination (PDF)