About occupational radiation exposure

Some Canadian workers may be exposed to radiation in the course of their daily work activities. It is therefore important for workers, especially pregnant women, to limit their exposure to radiation in their workplaces.

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Occupational exposure

Ionizing radiation is the type of radiation to which people who work in the nuclear industry or around x-ray equipment in medical institutions or laboratories are exposed.

A millisievert (mSv) is the unit used to measure the amount of radiation received. The amount of natural background radiation you receive each year in Canada is between 2 and 4 mSv.

The maximum amount of radiation people are allowed to receive in the workplace is regulated. The Canadian Nuclear Safety Commission sets a limit of 50 mSv in a single year and 100 mSv over 5 years (a 20 mSv per year average).

The limit for a pregnant worker, once pregnancy has been declared, is 4 mSv for the remainder of the pregnancy.

Provinces also have workplace radiation protection regulations, which vary from province to province. Radiation exposure limits are also set under the Canada Labour Code.

These various regulations and safe practices ensure that most people who are exposed to workplace radiation receive far below 20 mSv per year. While exposure levels vary by job, the average yearly radiation exposure of a monitored worker is about 0.3 mSv.

Pathways of exposure

There are two ways, or pathways that people can be exposed to radiation:

  1. Internal exposure occurs when radioactive dust or gases get inside the body and irradiate it from within. Radioactive particles can be inhaled, ingested or absorbed through the skin.
  2. External exposure occurs when a person has been physically close to a source of radiation. The penetrating radiation emitted by the source travels through the air and irradiates the person.

Knowing the pathway by which a person was exposed is important for determining the radiation dose received and appropriate monitoring is available for each of these pathways.

Minimizing risk of occupational radiation exposure

Many people who are exposed to radiation in the workplace wear a dosimeter, a badge that measures the accumulated exposure to radiation over a period of time, usually three months. A dosimeter can help ensure that best practices are followed to keep doses as low as can reasonably be achieved. Dosimeters are inexpensive and most employers supply them to workers exposed to radiation. In some jurisdictions dosimeters are required. A dosimeter will allow you monitor your exposure to radiation on a regular basis and will help occupational health specialists assess the risk in case of accidental exposure.

If you are pregnant, or thinking about becoming pregnant, you might also want to consider taking the following steps:

Monitoring workplace radiation exposure

The National Calibration Reference Centre for Bioassay and In Vivo Monitoring (NCRC) provides high quality intercomparison programs to validate measurement of internal ionizing radiation exposure of workers.

The National Dose Registry (NDR) is a centralized radiation dose record system operated by Health Canada which contains dose records of all monitored radiation workers in Canada.

The National Dosimetry Services (NDS) provides occupational monitoring for external ionizing radiation.

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