CDC Report Details Public Health Hazard in Flint, Michigan

Janis C. Kelly

June 27, 2016

The prevalence of blood lead levels (BLLs) at or above 5 μg/dL in children younger than age 5 years in Flint, Michigan, closely track with the use of drinking water from a local source, researchers from the Centers for Disease Control and Prevention (CDC) conclude in a study published June 24 in the Morbidity and Mortality Weekly Report.

After city officials switched from the Detroit Water Authority (DWA) to the Flint Water System (FWS), children were 46% more likely to have BLLs μg/dL than before the switch.

Lead investigator Chinaro Kennedy, DrPh, from the CDC's National Center for Environmental Health, suggests the spike in BLLs was caused by Flint Water System authorities' failure to use corrosion control, the absence of which is thought to have permitted lead to enter drinking water as a result of corrosion of lead pipes and or of lead solder used in "lead free" plumbing.

"This crisis was entirely preventable, and a startling reminder of the critical need to eliminate all sources of lead from our children's environment," senior author Patrick Breysse, PhD, director of CDC's National Center for Environmental Health, said in a CDC news release. "CDC is committed to continued support for the people of Flint through our Childhood Lead Poisoning Prevention program and efforts to raise awareness and promote action to address the critical public health issue in communities across the country."

About 99,000 residents of Flint were affected by changes in drinking water quality between April 25, 2014, and October 15, 2015. On January 2, 2015, Flint water customers received a water advisory notice after the state Department of Environmental Quality issued the city a notice of violation of the Safe Drinking Water Act because of excessive levels of trihalomethanes, contaminants formed as a byproduct of water disinfection.

Extended exposure to trihalomethanes has been associated with damage to the liver, kidney or central nervous system problems, and increased risk for cancer. The notice from the city warned residents with "a severely compromised immune system, [who] have an infant or are elderly" that they "may be at increased risk and should seek advice about drinking water from your health care provider."

Meanwhile, studies by local and national investigators found an increase in the prevalence of high BLLs in young children living in Flint.

On October 16, 2015, the water source was switched back to DWA, but residents were instructed to use only filtered tap water for drinking and for cooking, and that pregnant women, breast-feeding women, and children aged 6 years or younger should only drink bottled water.

Nearly 10,000 Samples Examined

The CDC investigators examined data from 9422 blood led tests in children aged 5 years or younger from three periods: before the switch in water source from DWA to FWS, during the switch (both before and after the January 2, 2015, water advisory), and after the switch back to DWA.

They found that 3.0% of children had BLLs at or above 5 μg/dL before the switch from DWA to FWS (April 25, 2013 - April 24, 2014) compared with 5.0% after the switch but before the water advisory (adjusted odds ratio, 1.46).

The prevalence of elevated BLLs dropped to 3.9% during the switch after the water advisory was issued, and dropped further to 1.4% after the switch from FWS back to DWA (October 16, 2015 - March 16, 2016).

Furthermore, the risk for elevated blood lead was significantly higher for children aged 1 to 2 years than in those younger than 1 year, and was significantly higher during summer and fall months than during winter months.

The authors explain, "Very young children consume more water per unit of body mass than do older children and adults, and they are more likely to engage in hand-to-mouth behaviors that put them at higher risk for exposure to lead in house dust and soil."

The CDC recommended that children younger than 6 years living in the City of Flint have their blood tested for lead by a healthcare provider, particularly if they have not had a blood lead test since October 2015, and that children with BLLs at or above 5 μg/dL be evaluated, including a home assessment for sources of lead.

The authors note that according to the US Environmental Protection Agency, Flint tap water is now safe to drink if it has been filtered through lead-certified water filters that are properly installed and maintained on household taps. They also note that Flint residents should continue to use filtered water for drinking, cooking, and brushing teeth. Regular household tap water can be used for bathing and showering because lead is not absorbed into the skin; however, parents should watch young children to prevent them from drinking bath water.

The authors have disclosed no relevant financial relationships.

MMWR Morb Mortal Wkly Rep. Published online June 24, 2016. Full text

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