WASHINGTON (May 13, 1998 09:20 a.m. EDT http://www.nando.net) - A new study linking lead in the drinking water of pregnant rats to damaged immune systems in their offspring could help explain why some human babies suffer from asthma and other allergies, researchers at Cornell University said Tuesday.
The researchers found that low levels of lead in rat embryos had no effect on the mothers but caused serious long-term immune system defects as the young rats matured. Their findings are also reported in the current issue of Toxicological Sciences.
Rodney Dietert, a professor at Cornell's College of Veterinary Medicine, said the young rats suffered immune changes due to the lead. The changes put them at increased risk for allergic diseases and reduced their immunity to tumors.
The Cornell researchers are conducting parallel studies on early lead exposure with embryonic chickens, but said they had no plans to extend the studies to humans, although there would be no shortage of possible subjects.
"Unfortunately, pregnant women even in this country are exposed to these levels of lead through drinking water, old paint and other sources," Dietert said. "And the situation is even worse in developing countries, where leaded gasoline is still sold and women work in factories where lead is used."
In the Cornell study, pregnant rats were given drinking water containing lead acetate in levels comparable to those humans might receive in water from old buildings with lead pipes and lead-based solder in pipe connections.
The fetuses and newborn rats exposed to lead grew just as fast as those rats without lead exposure, but showed significant and potentially harmful alterations in their immune systems when tested at 13 weeks of age, the researchers said.
"Based on these results, if there are key periods of early immune development which are particularly susceptible to persistent lead-induced alterations, it is possible that even short-term exposure of pregnant females, in rodents or in other species including humans, could compromise offspring immune function," the researchers wrote in the journal.
Researchers are focusing on a likely "window of susceptibility" during development when the immune system is assembling its defenses and disruption by lead could produce persistent damage.