Luke Waid drives 20 miles each day to shower at a relative's place, hauls bottled water back to his Flint, Michigan, home and worries about his 2-year-old daughter's irritability.
"I don't know if that is a product of her being exposed to high lead levels, or her just being a child," he said. "I’m not sure."
That uncertainty also presents a challenge to the lawyers who have enlisted as many as 1,800 residents, including Waid, as plaintiffs in lawsuits over contamination in the Flint's water supply.
The problem began in April 2014 when the city, then under the control of a state-appointed emergency manager, switched its water source to the Flint River from Lake Huron as a cost-saving measure, and corrosive river water caused lead to leach into the water supply. Flint switched back in October after tests showing elevated lead levels in the blood of some children became public.
In spite of the international outcry and the well-known toxic effects of lead, proving Flint's contaminated water actually caused any particular injury will be far from straightforward, lawyers with expertise in lead litigation said.
The difficulty in showing a causal link adds to other legal hurdles. State and city officials are challenging the cases, arguing they are protected by sovereign immunity, a legal doctrine that shields most government officials and agencies from liability for their official actions. That powerful defense already has kept many major plaintiffs firms away from Flint, since the water supply is government-run.
In an effort to overcome these potential obstacles, plaintiffs' lawyers are pursuing several strategies to seek redress for victims: individual lawsuits, class actions and a victims' compensation fund.
Plaintiffs' lawyers claim that the alleged government misconduct rose to the level of gross negligence or violated residents' constitutional rights, two exceptions to immunity. Some lawsuits also target private companies that performed work or tests on Flint's water system. The companies have denied responsibility.
It should be relatively easy to show in court that residents were exposed to lead, in part because government officials have publicly acknowledged the water is tainted, said Delaware Law School Professor Jean Eggen.
But exposure is not enough to prove damages, Eggen said. Lead injuries may not be apparent for years. In addition, injuries associated with lead poisoning - such as impaired brain development, reduced attention span and lower IQ - all have many causes.
New York law firm Napoli & Shkolnik said it has hired a Washington lobbyist to persuade Congress to create a compensation fund for Flint. Such funds may be set up to allow injured parties to receive compensation with a lower burden of proof than applicants would face in court. Napoli partner Hunter Shkolnik envisions such a fund paying for medical monitoring immediately, and possibly leaving the question of damages for later, putting money into people's pockets relatively quickly.
But Ken Feinberg, who oversaw victim compensation funds for victims of the Sept. 11, 2001 attacks and the 2010 BP Deep Horizon oil spill, is skeptical such an approach would work with Flint residents.
"How long do you monitor them?" asked Feinberg. "If they are deemed injured, are they injured by the water or by other means, other sources?"
The Napoli firm also is pursuing a class action in Michigan federal court. It said it has signed up some 800 clients and represents Waid in an individual lawsuit.
Corey Stern, a plaintiffs lawyer at New York's Levy & Konigsberg, said that he had filed individual cases in state court in Michigan on behalf of more than 100 children. He said the complexity of proving lead exposure caused specific injuries makes these cases better suited to individual lawsuits than class actions.
In 2013, a judge in Washington, D.C. ruled that a case over alleged lead contamination in the district's water supply would be unmanageable as a class action and should proceed as an individual lawsuit. The case is still pending.
Lead litigation in the U.S. to date has mostly involved children who have eaten chips of lead-based paint, or inhaled lead dust in the air or soil. The main defendants have been paint and lead manufacturers as well as landlords of properties containing lead paint.
The most clearcut cases involve children who develop serious learning disabilities or a measured drop in IQ within a few years of lead exposure.
In 2008, for example, Stern's firm won an $8.5 million verdict against New York building owners on behalf of a 15-year-old boy who was first exposed to lead paint and dust eight years earlier. His lawyers showed that he subsequently began failing all of his subjects and was classified as learning disabled, even though he had performed satisfactorily in kindergarten and first grade.
While the courts sort out the claims, residents like Waid and his daughter live with uncertainty. Though blood tests have shown she had elevated lead levels, the girl so far has no clear signs of injury - cold comfort for her father.
"If we knew that this was just her being a child and she was never exposed to lead, I wouldn't be worried at all," Waid said.
(Reporting by David Bailey; Editing by Anthony Lin, Amy Stevens and Lisa Girion)