Pollution control levels that affect the welfare of plants, animals, buildings and materials. Secondary standards may relate to either water quality or air pollution under the control of either the Safe Drinking Water Act or the Clean Air Act . These so-called "welfare effects" are thought not to affect human health but primarily crops, livestock, vegetation, and buildings. Secondary standards can refer to effects to which some monetary value could be ascribed, such as damage to materials, recreation , natural resources , community property, or aesthetics. Primary standards , on the other hand, refer to pollution levels that affect human health.