We often get asked about infant mental development and air pollution. Especially indoor air quality is an often overlooked source of exposure to pollution that can cause ill health and harm an infant's mental development. Far more attention is given to outdoor pollution. In fact, indoor air pollution may cause nearly 3% of the total global burden of disease, according to the World Health Organization. It makes sense – after all many of us spend up to 90% of our time indoors.
Cooking, either with solid fuel or gas, can be a major source of indoor air pollution, alongside cigarette smoke and fumes emitted from furniture, DIY products and office equipment. A new study from Spain shows how cooking with gas at home during pregnancy is linked with problems with infant mental development. The work was reported in the journal Epidemiology and described in Environmental Health News.
Babies born to mothers cooking with gas scored slightly lower on intelligence tests aged one and two compared to those who did not cook with gas. The fact that scores were better when there was an exhaust fan above the cooker does suggest (but not prove) a link with pollution from the stove.
All forms of combustion tend to produce nitrogen dioxide and the gas has already been linked with various health effects. Car exhausts are a major source of nitrogen oxide pollution and levels in cities are regularly measured using pollution monitoring networks. The levels of nitrogen dioxide indoors are not monitored.
Gas cookers use natural gas, propane or butane as fuels and produce nitrogen dioxide as one of their emissions, along with carbon monoxide and other gases. Levels of nitrogen dioxide are up to two times higher in homes with gas cookers.
Previous work has suggested that the presence of gas appliances in the home does have an effect on infant mental development at the age of four. This study involved more than 2,000 pregnant women who were asked what type of cooker they used (gas, electric or other) and whether they had an exhaust fan to deal with emissions. This question was asked during the third trimester of the pregnancy.
At age 11 months and 22 months, the Bayley Scale for infant mental development was used to assess the newborn's mental development. Infants with gas cookers present in their home scored about 2.5% lower than those whose families did not use gas. Note that this study just suggests a link. The actual level of the pollutants involved and their identity was not measured. Nor does this study tell us what the mechanism on the brain was that resulted in the lowering of intelligence scores. The research does, however, point the way towards further investigation of the impact of the presence of a gas cooker on infant brain development. This is particularly important because cooking with gas is so common.