1,3-Butadiene Environmental Exposures
1,3-Butadiene Environmental Exposures
Factors contributing to indoor levels of butadiene include cigarette smoke, proximity to a vehicle exhaust source (traffic or garage), cooking activity involving heated fats and oils (such as Chinese rapeseed, peanut, soybean and canola oils), wood burning, and natural gas/oil space heating.
Canada estimates that levels of 1,3-butadiene in outdoor air may also result in an increased risk of cancer (high data quality). Factors contributing to levels in outdoor air include forest fires, vehicle emissions, aircraft, marine and rail transportation, waste incinerator emissions, and thermal breakdown of butadiene-based rubbers and plastics.[1,2] Newer vehicles with catalytic converters emit less 1,3-butadiene than older vehicles.
Butadiene is not persistent in air and has an atmospheric half life of a few hours, depending on weather conditions. Levels in ambient air have been measured at several sites across Canada since 1987. Data published in 2006 indicates that the average 1,3-butadiene concentration from 2000-2003 was 0.22µg/m3 and 0.02 µg/m3 for urban and rural sites, respectively. The highest recorded 24-hour concentration was 2.58 µg/m3, measured near an industrial point source in Sarnia in 2001. Other industrial point sources where concentrations may be high include Yellowknife, Fort McMurray, Port Mellon, Montreal/Varennes, and Oakville. However, industrial emissions have declined since 2004.
There is currently little available data to indicate whether butadiene is present in drinking water, food, and soil in Canada. The potential for butadiene to migrate to food from containers exists, but is expected to be minimal; this route of exposure is likely much less important than inhalation.
Searches of environmental and consumer product databases yielded the following results on current potential for exposure to 1,3-butadiene in Canada:
NPRI and US Household Products Database
|Substance name: ‘1,3-Butadiene’|
|Released into Environment||26 t||Manufacturing (basic chemical; resin, synthetic
rubber, and fibres; petroleum and coal product),
oil and gas extraction,
pulp, paper and paperboard mills (21 facilities)
|Disposed of||0.049 t|
|Sent to off-site recycling||0.004 t|
t = tonne
|US Household Products 2016|
|Search Term||Quantity||Product Type|
|‘butadiene’||4||Roofing and cement adhesives|
This map shows predicted levels of 1,3-butadiene in outdoor air at residential locations by health region in Canada as of 2011. The average (median) concentration of 1,3-butadiene within the health regions measured in outdoor air for 2011 was 0.066 µg/m3, but concentrations of 1,3-butadiene can be higher or lower than average in many locations. Concentrations should be compared to the applicable jurisdictional guidelines and standards for ambient air quality based on chronic, carcinogenic effects (or non-carcinogenic effects, if cancer is not the point of interest).
Predicted annual average 1,3-butadiene concentrations in outdoor air at residential locations by health region, 2011
*Measured at the National Air Pollution Surveillance (NAPS) monitors in 2011
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 1,3-butadiene in relevant exposure pathways (outdoor air, indoor air, 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 1,3-butadiene 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
Compare substances: Canadian Potential Lifetime Excess Cancer Risk, 2011
The data in this table are based on average intake and Health Canada’s cancer potency factor, assuming no change in measured levels. When Health Canada values are not available, United States Environmental Protection Agency values are used.
Click the second tab to view LECR data.
**Exposure not applicable: For indicated pathways, substance not present, not carcinogenic, or exposure is negligible
**Gap in data: No cancer potency factor or unit risk factor, or no data available
IARC Group 1 = Carcinogenic to humans, IARC Group 2A = Probably carcinogenic to humans, IARC Group 2B = Possibly carcinogenic to humans
NOTE: Chromium (hexavalent) estimates assume that 5% of total chromium measured in outdoor air is hexavalent and 8% total chromium measured in indoor dust is hexavalent.
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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