Dichlorvos Environmental Exposures

Dichlorvos Environmental Exposures

Overview

The general public is most likely to be exposed to dichlorvos by inhaling contaminated air. CAREX Canada’s environmental estimates indicate that levels of dichlorvos in outdoor air do not result in an increased risk of cancer (very low data quality). Unfortunately, no recent data or studies were identified for dichlorvos levels in indoor air.

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The majority of environmental exposure to dichlorvos occurs through pest strips or sprays for insect control in homes and in
public.[1,2] Dichlorvos is not known to bioaccumulate in plants or animals.[3] It evaporates easily into the air and can break down via a reaction with water vapour (this reaction is faster under warm and humid conditions).[3] Dichlorvos may enter the environment through landfill waste contamination, accidental spills during transport, and leaks from storage containers.[3] Dichlorvos does not bind easily to soil and moves through it quickly. However, its breakdown in soil is slower than in air or water.[3] Therefore, skin contact may occur via contaminated soil. On dry hard surfaces it can persist longer; on wood, 39% of dichlorvos may remain for up to 33 days.[4]

Small amounts of dichlorvos residue have been detected in food.[2,3] However, the general population is expected to be minimally exposed to dichlorvos through food and beverages. The World Health Organization and the Food and the Agriculture Organization of the United Nations have designated 0 – 0.004 mg/kg of body weight as an acceptable daily intake (ADI) of dichlorvos.[4] Unfortunately, no data was available for dichlorvos levels in food or beverages. As a result, CAREX Canada was not able to conduct an adequate environmental exposure assessment for this exposure route.

Drinking water is a potential route for exposure to dichlorvos.[4] CAREX Canada’s environmental estimates indicate that levels of dichlorvos in drinking water result in an increased risk of cancer (low data quality).

Exposure may also occur in populations living near hazardous waste sites containing dichlorvos (usually in the form of liquid solution or as solid plastic pellets or strips) or sites where it is manufactured, processed, or stored.[3]

Dichlorvos is not reportable to the National Pollutant Release Inventory.[5] A search in the Household Products Database yielded five products, which included pest control strips and bed bug treatments.[6]

US Household Products Database

Search Term Quantity Product Type
‘Dichlorvos’ 5 Bedbug treatment, mosquito traps, pest control strips

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 dichlorvos in relevant exposure pathways (outdoor air, indoor air, indoor dust, 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 dichlorvos 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

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.

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

Supplemental data – Dichlorvos [PDF]

Sources

1. International Agency for Research on Cancer (IARC). Monograph summary, Volume 53 (1991) (PDF)
2. US Environmental Protection Agency (EPA). Dichlorvos (2007)
3. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Dichlorvos (1997) (PDF)
4. World Health Organization. Guidelines for Drinking-water Quality. Fourth edition. (2011) (PDF)
5. Environment and Climate Change Canada. National Pollutant Release Inventory (NPRI) Facility Search (Substance name: ‘Dichlorvos’)
6. US Household Products Database (HPD). Household Products (Search term: ‘Dichlorvos’)
 

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