More children in Pennsylvania had elevated levels of lead in their blood than 19 other states, according to data from the Centers for Disease Control and Prevention.

In 2014, 1.28 percent of children under the age of 3 tested positive for having an elevated amount of the toxic heavy metal in their blood, HealthGrove, a health information website, reported in an examination Wednesday.

Among the five counties in Southeastern Pennsylvania, Philadelphia had the highest percentage at 0.9 percent. Bucks County had the lowest at 0.3 percent. More than 33,000 additional children were tested in Philadelphia, however.

Southeastern Pennsylvania, where the majority of the state's population is centered, had some of the lowest levels across the commonwealth.

Warren County in Northwestern Pennsylvania and Blair County in Central Pennsylvania ranked highest.

Nationwide, among the 21 states that reported lead levels, New York was highest.

Other states with the highest levels were: Ohio, 0.96 percent; Rhode Island, 0.81 percent, Wisconsin, 0.77 percent; and Connecticut, 0.69 percent.

Also making the list: New Hampshire, 0.67 percent; Indiana, 0.54 percent; Vermont, 0.43 percent; Massachusetts, 0.37 percent and Maryland, 0.3 percents.

However, not all states report childhood blood-lead levels to the CDC, notes HealthGrove.

Elevated blood levels are defined as equal to or greater than 10 micrograms per deciliter of lead in blood for children. No safe blood-lead level in children has been identified, according to the CDC.

"Even low levels of lead in blood have been shown to affect IQ, ability to pay attention and academic achievement," the CDC website states. "And effects of lead exposure cannot be corrected."

Many cases of lead poisoning are traced to lead-based paint and are not solely the product of contaminated water.

Elevated lead levels can also be linked to contaminated water, as in Flint, Michigan, which attracted national attention when it was learned that the percentage of children age 5 and younger with elevated blood-lead levels had nearly doubled after the city switched its primary source of water to the Flint River.