Benzene in cars and other vehicles
We have completed this guidance in response to the recent spate of emails which have raised serious concerns about the levels of benzene which can building up within cars and other vehicles left in hot weather. In common with most of these types of emails there is an element of truth to this statement but what is the true story? Read on to find out.
Starting with the basics, it’s true that benzene is a toxic chemical known to produce a variety of ill health effects, including anaemia and cancer (specifically leukaemia) in humans. Benzene occurs naturally (typically as a component of crude oil) and you’ll also find it used in a range of products as a solvent (plastics, synthetic fibres, dyes, glues, detergents and drugs). It’s also a constituent of tobacco smoke and it present in petrol and petrol exhaust fumes.
Low levels of benzene are often present in outdoor air due to vehicles exhausts and industrial emissions. Vapours containing measurable levels of benzene are emitted by household products such as glues, paints, and furniture wax as products ‘gas off’. Due to this effect even higher levels of benzene can sometimes be found indoors, especially in new buildings with new fixtures and fittings.
Benzene in cars
Given the evidence above we have to conclude that dashboards, door panels, seats, and other interior components do emit benzene, as claimed in the email. In most cars these items will be made from plastics, synthetic fabrics and glues, some of which will have been manufactured using benzene may therefore “off-gas” trace amounts of benzene, particularly under hot conditions.
Most published studies where benzene levels have been measured inside vehicles have been done under typical driving conditions, i.e. in traffic. While such studies have found that benzene levels can significantly exceed those outside the vehicle and could pose a human health hazard, this is mainly attributed to the presence of exhaust fumes from other traffic.
Also, the amounts of benzene actually detected by researchers were significant but were far lower than the amounts that have been stated in these emails. A 2006 study reported in-vehicle benzene levels from exhaust fumes ranging from .013 mg to .56 mg per cubic meter — a far cry from the 400 mg to 4,000 mg reported.
Benzene levels in parked cars
In the one study found that took measurements of benzene levels inside parked cars with their engines turned off, the results were more benign. Toxicologists took samples of the air inside both a new and a used vehicle, under simulated hot-sunlight conditions, measuring the levels of volatile organic compounds (VOCs) including C3- and C4-alkylbenzenes, and exposing human and animal cells to the samples to determine their toxicity. Despite the detectable presence of VOCs (a total of 10.9 mg per cubic meter in the new car and 1.2 mg per cubic meter in the old car), no toxic effects were observed. Apart from noting the slight possibility that allergy-prone individuals might find their condition exacerbated by exposure to such compounds, the study concluded there is “no apparent health hazard of parked motor vehicle indoor air.”
When in doubt, ventilate
Despite this finding, some drivers may still be concerned about the presence of any benzene vapours inside their car, especially given the World Health Organization’s stated position that there is “no safe level of exposure” to the carcinogen. They may also worry that turning on the vehicle’s air conditioner might exacerbate their exposure to trapped toxins by recirculating contaminated air. If that’s the case, there’s no harm done — and much peace of mind to be gained — by simply opening the windows and ventilating the car before turning it on.