There's a reason doctors advise pregnant women to avoid eating fish -- there's a high risk that they are contaminated by mercury, a powerful neurotoxin to which pregnant women and children are particularly vulnerable.
How do fish end up full of mercury? Most commonly, fish are exposed to air pollution released by coal burning power plants, the largest source of mercury pollution. Mercury exposure has been linked to respiratory disease, birth defects, and developmental problems in children.
In 2011, the EPA released new regulations under the Clean Air Act in order to stem mercury pollution and other air toxins by requiring pollution controls on coal-burning power plants. The Supreme Court struck those regulations down yesterday, saying that the EPA had failed to look closely enough at the costs of the pollution controls before limiting emissions of mercury and other toxic pollutants from power plants.