Why your garage could pose a health threat
If you have a garage attached to your house, you could be at higher risk of developing leukemia or other forms of cancer.
Health Canada has expressed concern that benzene from car exhaust and other fumes could be entering homes. It’s now working on guidelines to help homeowners prevent the toxic gas from seeping into their homes.
Benzene is a volatile organic compound, or VOC, that’s found naturally in crude oil and thus in gasoline and vehicle exhaust.
There are already low levels of benzene in the air all around us due to air pollution from motor vehicle exhaust. But now Health Canada wants to make our homes safer.
Most Canadians know about the risks of carbon monoxide in their homes, but many aren’t as familiar with the risk of benzene exposure.
Deborah Schoen, the head of Health Canada’s indoor air section, says the agency has conducted studies measuring levels of the gas in homes across Canada. Those studies found that the levels were generally low, whether the houses had attached garages or not.
“On average, benzene levels in houses with attached garages are three times higher than of other houses,” Schoen told CTV News Channel this week from Ottawa.
Most drivers know not to run their vehicles after entering and closing the garage. What they may not know: after a car is turned off, the engine will continue to emit benzene into the air as it sits in the garage.
As well, the paints and solvents that many homeowners store in their garage also emit benzene as they slowly evaporate.
Schoen says that for the most part, the risk of long-term health effect is not high.
“The cancer risk is extremely low. But Health Canada and the World Health Organization and the European Commission recommend people reduce their exposure to benzene as much as possible,” she says.
“So for this reason, Health Canada advises people to reduce benzene exposure as much as possible.”
Studies have shown that benzene can definitely cause problems if people are exposed to high levels over long periods of time. Workers in industrial settings exposed to high levels of benzene have been shown to have a much higher risk of leukemia.
Benzene is dangerous because of the damage it can do to the blood. It causes bone marrow not to produce enough red blood cells, while also damaging the immune system by not creating enough white blood cells.
Thanks to regulations brought in in the 1990s that reduced the amount of benzene in gasoline, Canadians’ exposure to benzene has been dropping in recent decades.
But Schoen says it’s important to keep looking for ways to reduce our exposure to the gas even further, which is why Health Canada is focusing on the indoor air quality of homes with attached garages.
The guidelines are expected to advised homeowner to never idle a vehicle inside a garage, but to let it warm up outside.
“People might open the garage door and figure that’s enough,” Schoen said.
But even with the door open, a range of pollutants from vehicle exhaust– not just benzene but carbon monoxide and other pollutants-- accumulate when you idle your car in an attached garage.”
The next step should be to seal the walls and ceiling between the garage and home.
The Canada Mortgage and Housing Corp. provides a fact sheet on the risks of attached garages and offers these recommendations for minimizing the transfer of garage air to the home.
- Make sure the weather stripping around the door to the garage is continuous and in good shape.
- Have spray foam insulation installed to seal the wall between the house and garage. Then drywall can be installed over top to further reduce air leakage.
- A similar approach can be taken to seal the ceiling space between the garage and any rooms above. This will also help reduce energy costs and keep the floors warmer.
- Another approach involves installing an exhaust fan to vent garage air to the outside. The fan would also help depressurize the garage relative to the house, thereby preventing air movement from the garage to the house, even if leaks exist.