smoke and dust that choked Manhattan after the September 11, 2001 terrorist attack appears to have caused pregnant women to bear small babies. These are the findings of a study conducted by researchers from the us -based Mount Sinai School of Medicine. Women who were in the area on the day of the attack or up to three weeks later are more likely to have given birth to children with intrauterine growth restriction (iugr) as compared to females not exposed to the murky cloud. Babies born with iugr condition are small for the length of their gestation.

Trudy Berkowitz, who led the study, says the air pollution might be compared to cigarette smoke, which is known to reduce growth. "We don't really understand how cigarette smoking reduces birth weight, but we speculate that it affects oxygen levels or blood flow,' she says. The placenta would be particularly vulnerable because of its vital role in carrying oxygen to the foetus. The incident released a toxic cocktail of soot, benzene, polycyclic aromatic hydrocarbons, (pahs), heavy metals, pulverised glass and cement, and alkaline particulates into the lower Manhattan sky. Among all these pollutants, pah s are said to cause maximum damage. They are known to bind to the dna to form dna adducts in the white blood cells of the umbilical cord of mothers exposed to air pollution during pregnancy. The dna adducts are associated with reduced size of the newborns.

Berkowitz and colleagues studied 182 pregnant women. Twelve of them were in one of the towers of the World Trade Centre at the time of the attack. More than eight per cent of the these females had iugr babies compared with only 3.8 per cent of the mothers who were residing in areas of Manhattan that were not exposed to huge amounts of the toxic pollution. However, there were no significant differences between the two groups for factors such as mean birth weight, gestational age or pre-term births.

The researchers rule out post-traumatic stress disorder as a possible cause for the adverse effect. Berkowitz says the team will now study the children to assess possible long-term effects particularly on their cognitive and psychomotor development. Some babies with iugr never catch up with their counterparts and grow into lighter and smaller adults. "There may also be adverse neurological outcomes, like learning difficulties and hyperactivity,' explains Berkowitz.