Children are particularly at risk when it comes to lead exposure.
Small amounts of lead in adults are not thought to be harmful, but, even low levels of lead can be dangerous to infants and children.
Here is some key information from experts on the dangers of lead.
What are the sources of lead exposure?
Water is typically just one possible source of lead poisoning. Exposure can also come from lead-based paint, soil, household, dust, food, and certain types of pottery, porcelain, and pewter.
What problems can lead poisoning cause?
Too much lead in the body — lead poisoning — can cause serious damage to the brain, kidneys, nervous system, and red blood cells, potentially affecting physical development and the ability to learn.
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What level of lead is acceptable in children’s blood?
Lead levels in humans are typically measured in micrograms per deciliter of lead in the blood. Over the years, the threshold for when to be concerned has been lowered.
For example, the threshold was 40 micrograms per deciliter in 1971. Experts now say that blood lead levels of 5 or more micrograms per deciliter in children are considered to be elevated.
They also say that even lower levels can cause adverse health effects.
“No safe blood level has been identified,” the Centers for Disease Control and Prevention says on its website.
Has progress been made?
Blood test data tracked by the CDC shows that there have been big declines in the percentage of children in the US found to have elevated blood lead levels.
Data collected from 1976-1980 showed that 88 percent of children nationally under age 6 had levels of 10 micrograms per deciliter or higher. In 2014, just 0.53 percent did. In Massachusetts in 2014, the percentage was even lower, 0.37 percent.
What Massachusetts communities are most at risk?
The Massachusetts Department of Public Health tracks detailed municipal level data and has labeled certain towns and cities as being “high risk” for childhood lead poisoning, based on factors such as the rate of cases in the past five years, and the age of homes.
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The department gives a score to each such community.
The communities with the highest risk scores for the period from the start of 2010 to the end of 2014 were: Springfield, North Adams, New Bedford, Lawrence, and Brockton.
Other high-risk communities included Boston, Worcester, Somerville, Malden, Lynn, Holyoke, Chelsea, Lowell, and Fall River.
Matt Rocheleau can be reached at matthew.rocheleau@globe.com. Follow him on Twitter @mrochele