According to the Environmental Protection Agency (EPA), hazardous waste is generally classified into four main categories:

1. Characteristic Wastes: These exhibit at least one of four hazardous traits: ignitability (flammable, like gasoline), corrosivity (can rust or decompose materials, like car batteries), reactivity (unstable and can explode, like aerosol cans), or toxicity (harmful when ingested, like lead-based paint).

2. Listed Wastes: These are specific wastes from manufacturing and industrial processes that the EPA has officially designated as hazardous. They include byproducts from processes that use solvents, pesticides, and other chemicals.

3. Universal Wastes: These are commonly generated hazardous items that are subject to streamlined regulations. Examples include batteries, pesticides, mercury-containing equipment (e.g., bulbs), and some lamps.

4. Mixed Wastes: This category includes waste that contains both hazardous and radioactive components, making it subject to regulation by both the EPA and the Nuclear Regulatory Commission.

Determining if your water main contains lead involves a few steps. First, check the age of your property, as homes built before the 1980s might have lead pipes. Contact your water utility company for information on your service line material. Then, you can hire a professional plumber to conduct an inspection or use a lead testing kit to analyze water from the main line.

Lead toxicity comes from inhaling lead or consuming it. Before the 1980s, when the government banned lead from consumer use, it could be found in paint, plumbing, pipes, ceramics, and even gasoline. Lead paint is toxic for the same reason lead itself is toxic, which is why lead poisoning from paint presents the same as lead poisoning from water or food sources, with a slight increase in respiratory symptoms vs. digestive symptoms. Lead paint is most dangerous when it’s old and peeling, cracking, or otherwise disturbed. This increases the concentration in the air and, therefore, in breathable air. 

According to the EPA, there is no safe level of lead in the blood, and so the maximum contaminant level goal (MCLG) for lead in water is zero. Even at low levels, lead is harmful to human health. It can also remain in the body and build up over time with repeated exposure.