Case Studies in Toxicology: Drink the Water, but Don’t Eat the Paint
Case
A 2-year-old boy and his mother were referred to the ED by the child’s pediatrician after a routine venous blood lead level (BLL) taken at the boy’s recent well visit revealed an elevated lead level of 52 mcg/dL (normal range, <5 mcg/dL). The child’s mother reported that although her son had always been a picky eater, he had recently been complaining of abdominal pain.
The patient’s well-child visits had been normal until his recent 2-year checkup, at which time his pediatrician noticed some speech delay. On further history taking, the emergency physician (EP) learned the patient and his mother resided in an older home (built in the 1950s) that was in disrepair. The mother asked the EP if the elevation in the child’s BLL could be due to the drinking water in their town.
What are the most likely sources of environmental lead exposure?
In 2016, the topic of lead poisoning grabbed national attention when a pediatrician in Flint, Michigan detected an abrupt doubling of the number of children with elevated lead levels in her practice.1 Upon further investigation, it was discovered that these kids had one thing in common: the source of their drinking water. The City of Flint had recently switched the source of its potable water from Lake Huron to the Flint River. The lower quality water, which was not properly treated with an anticorrosive agent such as orthophosphate, led to widespread pipe corrosion and lead contamination. This finding resulted in a cascade of water testing by other municipalities and school systems, many of which identified lead concentrations above the currently accepted drinking water standard of 15 parts per billion (ppb).
Thousands of children each year are identified to have elevated BLLs, based on the Centers for Disease Control and Prevention definition of a “level of concern” as more than 5 mcg/dL.2 The majority of these exposures stem from environmental exposure to lead paint dust in the home, but drinking water normally contributes as a low-level, constant, “basal” exposure. While lead-contaminated drinking water is not acceptable, it is unlikely to generate many ED visits. However, there are a variety of other lead sources that may prompt children to present to the ED with acute or subacute lead poisoning.
Lead is a heavy metal whose physical properties indicate its common uses. It provides durability and opacity to pigments, which is why it is found in oil paint, house paint used before 1976, and on paint for large outdoor structures, where it is still used. Lead is also found in the pigments used in cosmetics, stained glass, and painted pottery, and as an adulterant in highly colored foodstuffs such as imported turmeric.3
The physicochemical characteristics of lead make it an ideal component of solder. Many plumbing pipes in use today are not lead, but join one another using lead solder at the joints, sites that are vulnerable to corrosion. The heavy molecular weight of lead makes it a useful component of bullets and munitions.
Tetraethyl lead was used as an “anti-knock” agent to smooth out the combustion of heterogenous compounds in automotive fuel before it was removed in the mid-1970s.4 Prior to its removal, leaded gasoline was the largest source of air, soil, and groundwater contamination leading to environmental exposures.4 At present, the most common source of environmental lead exposure among young children is through peeling paint in deteriorating residential buildings. Hazardous occupational lead exposures arise from work involving munitions, reclamation and salvage, painting, welding, and numerous other settings—particularly sites where industrial hygiene is suboptimal. Lead from these sites can be inadvertently transported home on clothing or shoes, raising the exposure risk for children in the household.4
What are the health effects of lead exposure?
Like most heavy metals, lead is toxic to many organ systems in the body. The signs and symptoms of lead poisoning vary depending on the patient’s BLL and age (Table 1).5 The most common clinical effect of lead in the adult population is hypertension.6 Additional renal effects include a Fanconi-type syndrome with glycosuria and proteinuria. Lead can cause a peripheral neuropathy that is predominantly motor, classically causing foot or wrist drop. Abdominal pain from lead exposure is sometimes termed “lead colic” due to its intermittent and often severe nature. Abnormalities in urate metabolism cause a gouty arthritis referred to as “saturnine gout.” 6
