Benzene Occupational Exposures

Benzene Occupational Exposures

Overview

The most important route of occupational exposure to benzene is inhalation, but dermal exposure can also occur.[1,2] Many workers are exposed to benzene via inhalation of motor vehicle exhaust.

CAREX Canada estimates that approximately 375,000 Canadian workers are exposed to benzene; most exposures occur in the low exposure category. Industries where the largest numbers of workers are exposed include automotive repair and maintenance, taxi and limo service, printing and related support services, public administration (where firefighters are included), and automobile dealers. According to the US Department of Labour, benzene exposure is also likely during petrochemical production, petroleum refining, coke and coal chemical manufacturing, tire manufacturing, and storage or transport of benzene and petroleum products containing benzene.[3]

Occupations at risk of benzene exposure include automotive service technicians and mechanics, delivery and courier drivers, taxi and limousine drivers, and firefighters. Other occupations such as steel workers, printers, rubber workers, shoemakers, laboratory technicians, and gas station employees were also identified as exposed.[3]

Prevalence Estimate

Results show that nearly 375,000 Canadians (approximately 2% of the working population) are exposed to benzene in their workplaces; 88% of these workers are male.

Industries with the greatest numbers of exposed workers are auto repair, taxi and limousine service, and the printing industry. Exposure to benzene in public administration is mostly attributed to the fact that firefighters are included in the industry.

When benzene exposure is examined by occupation, automotive service technicians and mechanics are the group with the greatest number of workers exposed to benzene (60,000). Other jobs with high numbers of workers exposed include delivery and courier drivers (51,000), taxi and limousine drivers (38,000), and firefighters (27,000). Other groups with significant numbers of workers exposed include motor vehicle body repairers, material handlers, truck drivers, and welders.

Workers exposed to benzene by industry

Alberta, Nova Scotia, Manitoba and Saskatchewan have a higher proportion of workers exposed to benzene than the national average (>2.3%), and Prince Edward Island, the Yukon and Nunavut have less workers exposed to benzene than the national average (<1.7%).

Workers exposed to benzene by region

Click the second tab to view total number of workers exposed.

* = < 50 workers

Level of exposure

In total, approximately 375,000 Canadians are exposed to benzene in their workplaces. The majority of workers exposed to benzene are in the low exposure category. A substantial number of benzene-exposed workers are at risk for moderate exposure, but very few are at risk of high exposure.

Level of Exposure by Industry

Identifying industries with either 1) workers exposed to high levels of benzene or 2) a larger number of workers exposed to benzene is important in guiding cancer prevention efforts to prioritize exposed groups and target resources most effectively.

The table below shows the number of workers exposed by industry group and level of exposure to benzene. These results highlight industries with the most number of workers, as well as industries with the highest levels of exposure. Data for those industries with at least 8,000 workers exposed is shown.

For example, in the repair and maintenance industry, all of the workers fall into the low exposure category. However, in the printing industry, a significant proportion (41%) of the exposed workers are in the moderate to high exposure category. Depending on the goals of a prevention campaign, exposure reduction in the large industrial group might be a useful strategy, or reducing exposure to those at highest risk of exposure could be seen as a priority.

*Numbers may not add up due to rounding

 

Methods and Data

Our Occupational Approach page outlines the general approach used to calculate prevalence and exposure level estimates for workplace exposures.

Data Sources

Data used in developing the occupational estimates for benzene were collected from several sources:

  1. The Canadian Workplace Exposure Database (CWED) contains over 1,500 measurements for benzene exposure. These measurements were collected during the years 1981 to 2004 in Ontario and British Columbia workplaces.
  2. Canadian and US scientific peer reviewed publications that addressed benzene exposure in Canada and the United States.
  3. Grey literature including technical reports from governments and international bodies.

Prevalence Estimate Method

CAREX defines exposure to benzene as inhalation exposure at work to levels above those encountered in the general environment.

To determine the number of workers potentially exposed to benzene at work, CAREX occupational exposure experts used methods previously established in other peer-reviewed CAREX projects in Europe. A series of steps were taken to assign exposure proportions to occupations and industries at risk of exposure to benzene.

  1. Occupations and industries at risk of possible exposure to benzene were identified using any combination of data sources described above.
  2. The total number of workers in each identified occupation and industry intersection was obtained from Statistics Canada 2006 census data.
  3. A percentage of workers exposed was assigned to that occupation and industry intersection. Percentages were determined by consultation with existing evidence in the data sources, previously established methods from the Europe CAREX estimates and the expert judgement of CAREX occupational hygienists.
  4. The number of workers in the identified group is multiplied by the assigned percentage to calculate the prevalence estimate of workers exposed to benzene.

 

Exposure Level Method

CAREX uses available workplace exposure measurements in the CWED to create exposure level categories by industry and occupation. For benzene, these categories are:

Category 1: Low Exposure

A group of workers (people in the same job category and industry) is put in this exposure category for one of two reasons:

  1. The are no valid measurements, but a hygienist identified this group as typically exposed during literature and other reviews;
  2. There are valid exposure measurements in the CWED and a hygienist review determined that exposure is plausible; AND EITHER:
    1. There are less than 10 samples available in the CWED, OR
    2. There are ≥10 measurements available but they do not meet the criteria for Moderate Exposure.

Category 2/3: Moderate to High Exposure

A group of workers is put in this exposure category if:

  1. There are at least 25 individual samples in the CWED, AND
  2. 20% or more samples have a value higher than 0.25 ppm (which is ½ of the current occupational exposure limit for benzene).

OR

  1. There are at least 10 individual samples in the CWED, AND
  2. 20% or more samples have a value higher than 0.5 ppm (which is the current occupational exposure limit for benzene).

For benzene, the moderate and high exposure categories were combined due to very few workers exposed above 0.5 ppm.

Sources

1. National Toxicology Program (NTP). 14th report on carcinogens for Benzene (2016) (PDF)
2. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Benzene (2007) (PDF)
3. Occupational Safety and Health Administration (OSHA). Benzene: Exposure Evaluation

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