By Jim Barlow Determining whether young children are at risk from potentially harmful lead contamination may be as easy as going to the family veterinarian, according to an extensive study of lead exposure in suburban St. Louis. For 80 years, until it closed in 1982, a smelting plant contaminated three Illinois towns near St. Louis. UI veterinary researchers report a strong link between blood lead levels of children who were under age 6 when they were tested in 1991 and their indoor pets. Children under 6 constitute the group most susceptible to cognitive damage resulting from lead contamination. "Based on our data, if blood lead concentrations were above 10 micrograms in dogs, then there was a 40 percent likelihood that a child in the same household had a high level," said Louise-Marie Cote of the UI College of Veterinary Medicine. "As a parent, I would want to have my child tested." The Centers for Disease Control has set 10 micrograms of lead in a child's blood as the threshold above which damage can occur. Some scientists argue that mental damage can occur at lower levels. A telling finding of the study was the relationship of family members' blood lead levels to the levels in their pets. "This is extremely important data," Cote said. "If your dog doesn't have a high level, you can be almost 90 percent confident that your household is safe." The study - part of a doctoral thesis by Philippe Berny, now with the Centre National d'Information en Toxicologie in Lyon, France - was published in June by the Hazardous Waste Research and Information Center in Champaign, which provided funding. It was co-written with Berny by Cote and William Buck, director of the UI's National Animal Poison Control Center. UI researchers focused on blood lead levels in 84 dogs and 26 cats in Granite City, while the CDC and the Illinois Department of Public Health sampled 827 residents. The U.S. Environmental Protection Agency, at the same time, studied the lead content in soils and house paint in the area that had been contaminated by the NL Industries plant, now an Environmental Protection Agency Superfund cleanup site. "Dogs and cats are at greater risk of exposure to the lead in the soil and dust," said Buck, who served on a National Academy of Sciences committee that wrote "Animals as Sentinels of Environmental Health Hazards," a book published in 1991 by the NAS Press. "They will pick up the lead first, and you can detect it in dogs earlier than in cats." Although 30 percent of the pets and 13 percent of the children under 6 had elevated levels of lead in their blood, none had suffered from symptoms of lead poisoning, Buck said. The authors of the study recommend that pets, especially dogs, be used as biological monitors in contaminated areas, and that veterinarians perform annual blood tests on the pets - a procedure that is easy, inexpensive and non-invasive - to guide health officials on the need to test children.