Silent Heavy Metal: Testing Lead

Old Paint on a Horse Cart
August 9, 2017

Lead poisoning has the highest rates among one- and two-year-olds, when kids are most likely to put their fingers in their mouths after crawling on floors with dust from lead paint.


It is silent, but sometimes present. When exposed, a child can be anemic or hyperactive, have a lower IQ or even hearing problems.

But those are pretty nonspecific symptoms. Physicians are more likely to test for lead exposure based on a person’s circumstances, notes Barbara Insley Crouch, executive director of Utah Poison Control Center, University of Utah Health.

SOURCES OF LEAD

Highly toxic to humans, lead is a blue-gray metal found in small amounts in the Earth’s crust. But because of human uses, it is found in other circumstances too—including in housing:

Children who live in buildings with pre-1979 lead-based paint in poor repair are in particular danger, and the Centers for Disease Control (CDC) has guidelines for testing them. At least 4 million households in the country have children being exposed to high levels of lead, says that agency. Half a million U.S. children between the ages of 1 and 5 have lead levels in their blood that exceed 5 micrograms per deciliter, the point at which the agency recommends public health officials take action. Lead poisoning has the highest rates among one- and two-year-olds, when kids are most likely to put their fingers in their mouths after crawling on floors with dust from lead paint.

When lead enters the body (usually as dust or in water), children’s stomachs and intestines absorb up to 50 percent of it, whereas those of adults absorb about 10 percent.

Other individuals who could be exposed include those:

  • working at or frequenting a firing range (where bullets contain lead)
  • living near mine tailings or auto yards with batteries
  • experiencing renovation in a pre-1979 house
  • playing in dirt fouled by years of leaded-gasoline car traffic
  • certain cultural factors: cosmetics or painted toys or trinkets from other countries; certain Ayurvedic medications from the Indian subcontinent; certain foods from other countries
  • making stained-glass art
  • using improperly glazed pottery or certain pottery from outside the country

WATER AND LEAD

While Flint, Michigan called attention to lead leached when an area’s water regulatory oversight was cut, serious contaminations have since occurred in water supplies in Ohio, Oregon, and elsewhere. We’re still working on moving away from water supply danger; as recently as 2014, an adjustment to the Safe Drinking Water Act reduced the maximum allowable lead content of pipes, pipe fittings, plumbing fittings, and fixtures to 0.25 percent. According to the EPA, at least 30 percent of our high-use water pipes in the U.S. are more than 40 years old.

David Grenache, PhD, medical director in the chemistry division at ARUP, says: “The testing is highly accurate, requiring special instrumentation and skill to be performed.”

One thing is clear: Humans, but especially children, are highly sensitive to any level of lead. At high levels of exposure, the metal attacks the brain and central nervous system, which can result in coma, convulsions and death. Children who live with severe lead poisoning may suffer mental retardation and behavioral disorders, according to the World Health Organization (WHO).

But risk-wise, why are children affected more quickly and seriously? When lead enters the body (usually as dust or in water), children’s stomachs and intestines absorb up to 50 percent of it, whereas those of adults absorb about 10 percent. Also, children who are deficient in iron, calcium, and certain other nutrients absorb lead more readily, according to several studies on the CDC website.

TESTING

When tested, a person’s blood-lead level (BLL) is measured from a finger-prick or venous blood draw. In the testing at major laboratories such as ARUP, a method called quantitative inductively coupled plasma-mass spectrometry (ICP-MS) measures lead in blood in micrograms per deciliter. This technique is capable of detecting metals and several non-metals with high analytical sensitivity and specificity. David Grenache, PhD, medical director in the chemistry division at ARUP, says: “The testing is highly accurate, requiring special instrumentation and skill to be performed.”

Catherine Arnold, Science Communications Writer