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ask joanne

My daughter has an air freshener hanging from her rear-view mirror. I've told her it's not good to have things obstructing her view, never mind the irritating smell. Aren't these things potentially hazardous? – Jennie in Port Hardy, B.C.

Anything obstructing a driver's field of view is obviously dangerous. Larger items such as teddy bears and CDs dangling from rear-view mirrors have been known to impair vision, but air fresheners aren't typically an issue.

Safety experts I contacted in the United States and Canada had little data on this. In Britain, a 2011 AA survey found that 5 per cent of motorists had objects hanging from the rear-view mirror that could potentially obstruct their view.

"The piece of kit traditionally hanging from rear-view mirrors is furry dice, but it's gotten worse over the years with the introduction of sat navs," says an AA spokesperson. "Quite often, you see people with one stuck to the centre of their windscreen, which is dangerous. Air fresheners, from our point of view, are the least of the problem."

Whether you prefer the available scent of bacon, or classic vanilla – it's the composition of some air fresheners that may be cause for concern.

"These air fresheners in cars can emit potentially hazardous chemicals, ones that are linked with asthma attacks, breathing difficulties, dizziness and migraine headaches," says Dr. Anne Steinemann, a civil and environmental engineer currently a program manager and visiting researcher at the University of California in San Diego, who has studied pollutant exposures and health effects.

"I've analyzed a range of air fresheners in terms of solids, oils, gels and sprays and I have found that all of the air fresheners I tested – even ones called green or organic or all-natural or non-toxic – emit chemicals classified as toxic or hazardous," says Steinemann.

According to the Canadian Centre for Occupational Health and Safety, products such as cleaners and air fresheners sold to the general public require consumer labelling only. Because this type of label focuses on immediate hazards such as corrosive properties (burns to skin and eyes), explosion, fire and poison, only certain ingredients will be listed.

Steinemann found that fewer than one per cent of the chemicals she discovered in the products she tested were disclosed on the labels. "So the public has no way of knowing what's really in an individual air freshener," she says.

Steinemann found substances such as acetaldehyde and acetone, which are classified as toxic or hazardous in the United States and Canada, in the air fresheners tested. It's important to understand that toxicity depends not only on the individual chemicals, she adds, but on interactions between the chemicals.

"And for some people even low levels of chemicals can result in adverse health effects," says Steinemann.

To find out the full list of ingredients in a product, try contacting the manufacturer.

In the meantime, you may want to pass Steinemann's advice on to your daughter: "Instead of using an air freshener, deal with the problem directly. Open up the windows, use ventilation rather than a product that emits potentially hazardous chemicals and masks the problem rather than improve the air quality."

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