Democratic presidential candidates said lead contamination in Flint’s drinking water shows how lagging federal infrastructure investment can be dangerous for black and brown communities.

Flint’s drinking water crisis came up several times during a Nevada infrastructure forum in Nevada attended by former Vice President Joe Biden, former South Bend, Ind. mayor Pete Buttigieg, U.S. Sen. Amy Klobuchar, D-Minn., and billionaire activist Tom Steyer. The candidates expressed a commitment to environmental justice, saying people of color are disproportionally affected by lead contamination and other issues related to aging infrastructure.

Problems for Flint, a majority-black city, began in 2014 when state and local officials agreed to switch the city’s water supply to the Flint River. Complaints about the quality of the new sources rose within weeks and it was eventually determined that officials failed to treat corrosive water from the Flint River, causing lead to leach into drinking water.