Sunday, 30 December, 2001, 02:50 GMT: BBC News
Pollution linked to birth defects
Women exposed to high levels of ozone and carbon monoxide may be up to three times as likely to give birth to a baby with heart defects, American research suggests.
Scientists found the risk increased when women were exposed to high levels of the pollutants in the second month of their pregnancy.
That is the time when the heart and other organs begin to develop.
The research team suggest this is the first “compelling evidence” air pollution may play a role in causing some birth defects.
The research was carried out at the University of California Los Angeles (UCLA) School of Public Health and the California Birth Defects Monitoring Program (CBCMP)
Beate Ritz, a UCLA epidemiologist, who led the study, said: “The greater a woman’s exposure to one of these two pollutants in the critical second month of pregnancy, the greater the chance that her child would have one of these serious cardiac birth defects.”
Previous research by the same team has linked air pollution to harmful effects on pregnancy, including giving birth prematurely and low birth-weight babies.
Ozone gas is present in photochemical smog – produced by chemical reaction under ultraviolet light from the Sun.
Carbon monoxide is a colourless, odourless gas produced as a by-product of combustion – in vehicle exhaust fumes, for example.
Air quality checks
The study, published in the American Journal of Epidemiology, looked at information on more than 9,000 babies born between 1987 and 1993 in Los Angeles, Orange, San Bernardino and Riverside counties from the CBCMP.
They compared air quality near the children’s homes to that in the areas where healthy children lived, using measurements from the South Coast Air Quality Management District.
They found that pregnant women who were exposed to increased levels of ozone and carbon monoxide faced an higher risk of having a child with conotruncal heart defects – a group of severe heart problems, pulmonary artery or valve defects and aortic artery or valve defects.
Women who lived in areas with the highest levels of the pollutants had three times the risk of those living in areas with the cleanest air.
For women who lived in areas with moderately higher pollution, the risk of birth defects doubled.
This group of heart defects occurs 1.76 times per 1,000 births. Many babies need open-heart surgery before age one.
Cause for concern
Dr Ritz said: “These findings show that there are more health problems caused by air pollution than solely asthma and other respiratory illnesses.
“There seems to be something in the air that can harm developing foetuses.”
She added that although there had been a significant in ozone and carbon monoxide levels, there may be “secondary pollutants” occurring alongside the gases which were not yet measured or understood, and which could themselves pose health risks.
Gary Shaw of the CBCMP, who also worked on the research admitted: “We¿re not sure carbon monoxide is the culprit because it could be just a marker for something else in tailpipe exhaust.
“The fact that certain heart defects are turning up in the second month of pregnancy when hearts are being formed suggests something serious may be happening.
He called for further research: “Unlike other health factors like diet or lifestyle, a pregnant woman has almost no control over the quality of air she breathes – we need answers.”
The researchers admit the study is limited because it could only assess pregnant women’s exposure to pollutants by checking measurements of certain pollutants at monitoring stations, which could be up to 10 miles away.
They were also unable to look at other risk factors for birth defects, including maternal smoking, occupational exposures, vitamin supplement use, diet and obesity.