Stormwater Pollutants of Emerging Concern
Stormwater discharges contain pollutants from a variety of sources. These pollutants may pose newly identified or reemerging risks to human health, aquatic life, or the environment. These substances, sometimes referred to as emerging contaminants, can include many different types of natural or manufactured chemicals and substances.
Stormwater dischargers may:
- Manufacture substances that are considered emerging contaminants;
- Use products or materials that contain emerging contaminants or substances that break down to become emerging contaminants; or
- Manage stormwater from areas where products or materials containing emerging contaminants or substances that break down into emerging contaminants are used or stored.
When these materials come into contact with stormwater from rainfall or snowmelt, they can dissolve into the stormwater or stick to sediments in the stormwater. Stormwater can then transport emerging contaminants and discharge them into nearby waterways. Emerging contaminants may be present in stormwater discharges and should be considered when designing stormwater control measures and management strategies. Some examples include:
- Per-and Polyfluoroalkyl Substances (PFAS): PFAS are a group of manufactured chemicals that are used for their properties to resist heat, oil, stains, grease, and water. PFAS are used in a variety of products and processes, including clothing, furniture, metal finishing, electroplating, electronic components, adhesives, food packaging, heat-resistant non-stick cooking surfaces, molded plastic, and the insulation of electrical wire.
- Polycyclic Aromatic Hydrocarbons (PAHs): PAHs may have either natural or man-made sources. Natural sources include wildfires, volcanic eruptions, and degradation of materials within sediments and fossil fuels. Man-made sources include the incomplete burning of organic materials like coal, oil, gas, wood, and garbage, vehicle exhaust, asphalt, coal-tar based pavement sealcoat, and creosote.
- Microplastics: Microplastics are plastic particles that are generally less than 5 mm in size. Examples of microplastics include pre-production plastic pellets known as “nurdles” and microbeads, both of which are used in some personal care products. Microplastics may also come from the breakdown of larger plastics.
- 6PPD and 6PPD-quinone: 6PPD is an additive to rubber components, most notably in all types of tires, but can be in belts, hoses, cables, and automotive mounts. 6PPD is added to prevent the rubber from breaking down due to reactions with ozone and other reactive oxygen species in the air. When 6PPD reacts with ozone (O3), it forms into 6PPD-quinone.
- Pharmaceuticals and Personal Care Products (PPCPs): PPCPs are increasingly being detected at low levels in surface water and include over-the-counter medications, fragrances, sunscreen, detergents, preservatives, and insect repellents.