PORTLAND, Ore. (KOIN) — Even though lead-based paint was banned for home use in 1978, it’s still in homes built before then. Each year, Multnomah County finds as many as 100 children a year who are victims of lead poisoning.

Lead poisoning is the Number One threat to kids in homes. Now, researchers at OHSU say it only takes a small amount of lead to increase the risk of ADHD.

There’s always been a suspicion lead and ADHD were connected, but this study said there is a definitive link.

Perry Cabot, a lead specialist with Multnomah County, Jan. 7, 2016 (KOIN)

This study “is the first to confirm previous hypotheses that exposure to lead in miniscule amounts typical in the U.S., or less than 10 parts per billion, increases symptoms in some individuals with ADHD.”

Multnomah County provides testing at some of its health clinics to check lead levels in those most at risk — children under the age of 6 and pregnant and nursing women.

Lead poisoning may not cause immediate symptoms but it can cause permanent brain damage, especially in young children as their brain is rapidly developing.

But it’s not just pre-schoolers at risk. Older kids and adults who can inhale lead dust are at risk when remodeling is underway.

There’s also a concern about lead found in drinking water. Perry Cabot, a lead specialist with Multnomah County, said it’s best to let your water run for about 30 seconds — preferably cold, he said — after you’ve been gone from your home all day.

Sample testing is also offered through Multnomah County for Portland Water Bureau customers. Some states require blood testing for lead for children, but Oregon and Washington do not.

Parents can ask a pediatrician to test for lead.

Lead check swabs are used to detect lead levels in household items, Jan. 7, 2016 (KOIN)