Naturally occuring radiation: an emerging occupational health issue.

Everybody knows that radiation can be a health hazard. As a consequence, procedures to reduce radiation exposure from sources such as x-rays, medical wastes or working in the nuclear and uranium industries are well established.

Most important sources of radiation exposure result from human activities such as mining or health care, but there are other very common sources of radiation which occur naturally in the environment. Most of us would be surprised to know, for example, that plants, animals and even the human body contain traces of radioactive elements such as potassium-40.

The risk from naturally occurring radioactive material (NORM) is typically so low that it poses no risk to human health; however, in several industries NORM can be concentrated at levels which may pose a health hazard to some workers.

Our understanding of this category of occupational health and safety risk has emerged quite recently. Health Canada's first set of guidelines for the management of NORM came out late in 2000.

While the risk to the general public from NORM is negligible, certain categories of workers can be exposed to unnecessary risk. Higher risk industries operating in Saskatchewan include oil and gas distribution and electrical production using coal.

Why is there an occupational health risk from NORM in the oil industry? Oil contains NORM in minute amounts that may not even be detectable and pose no health hazard. However, as millions of barrels of oil are delivered through pipelines over long periods of time, radioactive material may be concentrated in the scale that builds up on the inside of pipes. Pipe scale tends to accumulate on pumps or other parts that deteriorate from wear and tear; when workers service these parts, they may be exposed to a radiation risk.

The radiation in pipe scale itself may be quite low, but if it is breathed into the lungs as dust, alpha radiation may cause cellular damage and increase the risk of cancer. So long as workers are made aware of the problem the risk is low, since prevention may be as simple as wearing a dust mask and changing clothes and showering after work.

Another industry where risk may occur is scrap metal recycling. Workers who salvage pipe from the oil industry, for instance, may be advised to take simple precautions to avoid breathing in dust from pipe scale. Any industry concerned about NORM can contact occupational health and safety officials about the advisability of testing to determine whether there is a significant level of risk.

There is also some potential for the concentration of NORM in the production of electricity from coal. Since all living things contain NORM and coal is a concentrated form of carbon from plants and animals, it may contain concentrations of NORM. Ash from burning coal in thermal electricity generation does contain measurable amounts of uranium.

Today, coal-fired power plants collect all or most of the ash produced, preventing the spread of radiation through the atmosphere. However, precautions will be required in the use and storage of ash, which could have higher than acceptable levels of radioactivity. The same problem may also occur in the forest products industry, where ashes left from combustion of wood wastes may concentrate the NORM naturally present in wood.

One additional area of concern is the importation of products that could contain NORM in higher than acceptable amounts. Phosphate fertilizer is one product that may contain higher concentration of NORM if the source ore has elevated NORM. Products imported from countries that do not segregate hazardous wastes could contain unacceptable levels of NORM, if certain wastes such as scrap metal are recycled to make new products.

In general, we are in the enviable position with NORM, given that a potential health concern is being identified ahead of any visible problem among workers. By recognizing a potential problem, it is now possible for industries with some level of risk to protect their workers using fairly simple, low-cost methods.

Wo Yuen, Ph.D., is a Laboratory Manager with the Saskatchewan Research Council's Analytical Laboratories.