Tracking reduction of water lead levels in two homes during the Flint Federal Emergency.

A Federal Emergency was declared in Flint, MI, on January 16, 2016, 18-months after a switch to Flint River source water without phosphate corrosion control. Remedial actions to resolve the corresponding lead in water crisis included reconnection to the original Lake Huron source water with orthophosphate, implementing enhanced corrosion control by dosing extra orthophosphate, a "Flush for Flint" program to help clean out loose leaded sediment from service lines and premise plumbing, and eventually lead service line replacement. Independent sampling over a period of 37 months (January 2016-February 2019) was conducted by the United States Environmental Protection Agency and Virginia Tech to evaluate possible human exposure via normal flow (∼2-3 L/min) sampling at the cold kitchen tap, and to examine the status of loose deposits from the service line and the premise plumbing via high-velocity flushing (∼12-13 L/min) from the hose bib. The sampling results indicated that high lead in water persisted for more than a year in two Flint homes due to a large reservoir of lead deposits. The effects of a large reservoir of loose lead deposits persisted until the lead service line was completely removed in these two anomalous homes. As water conservation efforts are implemented in many areas of the country, problems with mobile lead reservoirs in service lines are likely to pose a human health risk.

Residential water heater cleaning and occurrence of Legionella in Flint, MI.

After the Federal emergency in Flint, MI was declared in early 2016 in response to elevated lead-in-water and incidence of Legionnaires' disease, concerns arose that contaminants in residential water heaters could continue to contribute to poor quality tap water. Here, a comprehensive field survey of residential water heaters (n = 30) and associated water quality was conducted and the subsequent effects of an aggressive manual water heater clean-out was determined, including draining the tank and removing sediments via brushing and flushing. Before cleaning, inorganics accumulated in the tank sediments did not serve as a source of metals measured at hot water outlets. After cleaning, hardness- (calcium, magnesium, silica) and corrosion-associated inorganics (lead, iron, copper, aluminum, zinc) decreased by 64% in samples from sediment cleanout drain valves. Culturable L. pneumophila was only detected in 1 home (3.3%) prior to cleaning and 2 homes (6.7%) after cleaning, thus quantitative polymerase chain reaction was used to quantify potential effects on unculturable strains despite the limitation of differentiating live and dead cells. After the cleaning protocol, Legionella spp. and L. pneumophila gene numbers decreased or remained non-detectable in 83% and 98% of samples, respectively. Homes with less than 0.4 mg/L influent free chlorine tended to have quantifiable Legionella spp. gene numbers in water entering the home and had elevated L. pneumophila and Legionella spp. gene numbers throughout the home plumbing. Also, Legionella spp. and L. pneumophila gene numbers were highest for water heaters set at or below ∼42 °C and significantly decreased >51 °C, consistent with Legionella's preferred temperature range. Examination of the only home that had culturable L. pneumophila both before and after the cleaning protocol revealed that the organism was culturable from several sample locations throughout the home, including in water representative of the water main. Notably, the home was located in close proximity to McLaren Hospital, where an outbreak of Legionnaires disease was reported, and the water heater had a setpoint within the Legionella growth range of 44.2 °C. Considering that other factors were more strongly associated with Legionella occurrence and water heater sediment was not detectably mobilizing to tap water, it was concluded that water heater cleaning had some benefits, but was not an overarching factor contributing to possible human health risks.

Showering in Flint, MI: Is there a DBP problem?

Lead contamination in the City of Flint, MI has been well documented over the past two years, with lead levels above the EPA Action Level until summer 2016. This resulted from an ill-fated decision to switch from Detroit water (Lake Huron) with corrosion control, to Flint River water without corrosion control. Although lead levels are now closer to normal, reports of skin rashes have sparked questions surrounding tap water in some Flint homes. This study investigated the presence of contaminants, including disinfection by-products (DBPs), in the hot tap water used for showering in the homes of residents in Flint. Extensive quantitative analysis of 61 regulated and priority unregulated DBPs was conducted in Flint hot and cold tap water, along with the analysis of 50 volatile organic compounds and a nontarget comprehensive, broadscreen analysis, to identify a possible source for the reported skin rashes. For comparison, chlorinated hot and cold waters from three other cities were also sampled, including Detroit, which also uses Lake Huron as its source water. Results showed that hot water samples generally contained elevated levels of regulated and priority unregulated DBPs compared to cold water samples, but trihalomethanes were still within regulatory limits. Overall, hot shower water from Flint was similar to waters sampled from the three other cities and did not have unusually high levels of DBPs or other organic chemicals that could be responsible for the skin rashes observed by residents. It is possible that an inorganic chemical or microbial contaminant may be responsible.