Dichloromethane Environmental Exposures

Dichloromethane Environmental Exposures

Overview

An estimated 80% of dichloromethane produced globally is released to the environment.[1] Based on data gathered in the early 1990’s, indoor air is likely the most significant source of exposure for Canadians.[2] CAREX Canada’s environmental estimates indicate that dichloromethane levels in indoor air result in an increased risk of cancer (moderate data quality).

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Ambient air may be of greater concern in industrialized urban areas and in close proximity to waste or disposal sites.[1,3]CAREX Canada’s environmental estimates indicate that dichloromethane levels in outdoor air do not result in an increased risk of cancer (high data quality).

Environment Canada estimated that 2 million people were exposed to dichloromethane by using consumer products including paint strippers, aerosol paints, and insecticides and cleaning solutions.[4] Data on levels of dichloromethane in food is limited; however, it has been detected in several products including cereal and butter.[2,5] Potential for bioaccumulation in foods is low.[5] Dichloromethane levels are below the detection limit in the majority of drinking water samples collected in Canada, and are more frequently associated with groundwater sources.[5,6]  Total daily intakes of dichloromethane for the Canadian general population are estimated to range from 3.96 to 6.62 micrograms/kilogram of body weight per day.[2] No recent Canadian studies have been identified for dichloromethane estimates in food and beverages.

Soil data on dichloromethane levels is limited to contaminated sites.[2,5]Dichloromethane has been detected in groundwater in Canada, and is usually associated with nearby landfills and waste disposal sites.[2]

Searches of the National Pollutant Release Inventory (NPRI) and US Household Products Database yielded the following results on current potential for exposure to dichloromethane in Canada:

NPRI and US Household Products Database

NPRI 2015[7] 
Search term: ‘dichloromethane’
Category Quantity Industry
Released into Environment 20 t Office furniture manufacturing,
pharmaceutical and chemical manufacture,
pulp and paper mills,
paint, coating and adhesive manufacturing
(24 facilities)
Disposed of 328 t
Sent to off-site recycling 267 t
US Household Products 2015[8] 
Search Term Quantity Product Type
‘Methylene chloride’ 55 Heavy-duty automotive cleaners and degreasers (11),
paint and adhesive remover (39),
paint brush cleaner (2), furniture cleaner (1),
deglosser (1), and herbicide (1)
t = tonne

Mapping

This map shows predicted levels of dichloromethane in outdoor air at residential locations by health region in Canada as of 2011. The average (median) concentration of dichloromethane within the health regions measured in outdoor air for 2011 was 0.530 µg/m3, but concentrations of dichloromethane 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 dichloromethane 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 dichloromethane 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 dichloromethane 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

Our Environmental Approach page outlines the general approach used to calculate lifetime excess cancer risk estimates and includes documentation on our mapping methods.

Data sources and data quality for dichloromethane can be found in the PDF below.

Supplemental data – Dichloromethane [PDF]

Sources

3. National Toxicology Program (NTP). 14th Report on Carcinogens for Dichloromethane (2016) (PDF)
6. Conestoga-Rovers & Associates. Drinking Water Survey for New Parameters of Interest/Concern (2014) (PDF)
7. Environment and Climate Change Canada. National Pollutant Release Inventory (NPRI Facilty Search (Substance name: ‘Dicholoromethane’)
8. US National Library of Medicine. Household Products Database (HPD) (Search term: ‘Dicholoromethane’)
        

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