On Wednesday, the US Environmental Protection Agency released the first nationwide guidelines to determine the dangerous levels of algal toxins in public water systems.

According to EPA, up to 48 million people nationwide get drinking water from lakes and reservoirs that could become polluted with toxins generated by algae-like bacteria.

Last August, pollution from cyanobacteria in Lake Erie left more than 400,000 people in northwestern Ohio and southeastern Michigan without usable tap water for two days.

Scientists believe that the problem behind the rising number of algae contamination cases is due to climate change and higher levels of nutrients such as phosphorus.

Administrator Gina McCarthy mentioned that best available science is used by EPA to propose guidelines, which ensure the safety of America's drinking water.

She said, "We will work closely with our partners at the state and local levels on monitoring, treating and communicating about the toxins, as well as addressing the sources of nutrients that fuel these harmful algal blooms".

A consistent national standard for algal toxins in drinking water has been made mandatory by many state and local officials. The EPA stopped short of a mandatory ceiling, instead identifying thresholds above which human health could be endangered.

Standard guidelines can be used by water-plant operators and other officials to trigger actions such as stepped-up monitoring, treating water to reduce toxins or issuing health advisories.

The guidelines focus on two common toxins, microcystin and cylindrospermopsin, which are produced by blue-green algae. They can cause vomiting, diarrhea and other symptoms and have killed dogs and livestock. Their prolonged exposure can damage liver and kidneys.

Peter Grevatt, agency's top regulator for groundwater and drinking water, said a separate standard has been set for young children as they drink more water per body weight than older children and adults.