Ten minutes spent in car with a smoker increases a child's exposure to harmful pollutants by 30 percent, reveals study.
Pollutant levels exceeded those found in restaurants, bars, and casinos, the study showed.
The researchers base their findings on 22 assessments of the air quality inside a stationary vehicle after three cigarettes had been smoked over the course of an hour.
On each occasion, levels of pollutants that are normally emitted by cars as well as by cigarettes, were measured in the back seat of a vehicle at the breathing height of a child-with the front windows completely down (position 1), and again with the windows open just 10 cm (position 2).
These pollutants were also measured outside the vehicle and included particulate matter, polycyclic aromatic hydrocarbons (PAH), and carbon monoxide, plus nicotine.
Exposure to PAH, in particular, has been linked to immune system disturbances, wheeze, IQ changes, and allergic sensitisation, the researchers said.
The pollutant levels inside the car at both window settings were three times as high as those measured outside, the results showed.
The average particulate matter levels inside the car were 746.1 micro g/m3 at position 1 and 1172.1 micro g/m3 at position 2. The average size of the particulate matter was 0.3 um.
Average levels of carbon monoxide reached 2.8 parts per million when cigarettes were extinguished, while those of PAH were around 10 times as high inside the car as they were outside.
Nicotine levels varied between 5.06 micro g/m3 and 411.3 micro g/m3 for both window positions inside the car.
On the basis of their findings, the researchers calculated that spending even a short amount of time inside a car with a smoker would make a significant difference to a child's daily exposure to harmful pollutants.
Just 10 minutes at 1697 micro g/m3 would increase a child's average daily exposure to particulate matter by up to 30 percent, and by 18 percent at levels of 1000 micro g/m3, the researchers estimated.
They pointed out that levels of harmful pollutants found inside the car exceeded those found in restaurants, bars, and casinos.
The researchers concluded that their findings support moves to restrict this type of exposure in cars, especially those carrying children.
The research has been published online in Tobacco Control.