August is Water Quality Month, so it’s fitting that the Environment and Public Works Senate subcommittee held a hearing to better understand the potential environmental impacts of a common tire additive to waterways on July 31, 2024. Through wear and tear, the tire additive 6PPD creates a toxic byproduct, 6PPD-quinone (6PPD-q). The impact of 6PPD-q on the environment is still under investigation.
Toxic Tires: A Deadly Threat to Aquatic Animals
The common tire additive 6PPD, used to prevent tires from cracking and degrading due to ozone exposure, is one of the emerging threats to aquatic animals. This chemical reacts with ozone to form 6PPD-quinone , which is released from tires through normal wear and tear. Tire dust results from friction between tires and roadways while driving and braking, resulting in 6PPD-q dust accumulation on roadways where stormwater runoff can carry it to contaminate waterways and aquatic habitats.
6PPD-q is highly toxic to some aquatic animals. Research has shown that 6PPD-q can cause death to coho salmon within hours of exposure in stormwater, even at very low concentrations. This toxicity also affects other aquatic life, including other fish and the major predator of Coho salmon, the endangered Southern Resident orca. 6PPD-q is ubiquitous: it can be found in Native American tribes that depend on salmon in their diet and found in the urine of pregnant women. The impact on humans is not yet known.
Other aquatic species, such as Brook trout, Lake trout, Rainbow trout, and White-spotted char (in Japan and East Asia) are susceptible to 6PPD-q. Future US Geological Survey research plans to investigate the impact of 6PPD-q on aquatic animals in identified potential “hot spots” across the country for a better understanding of its long-term impact.
Research and Planning to Protect Aquatic Animals
The U.S. Environmental Protection Agency (EPA) recently developed a draft testing method (EPA Method 1634) that can detect 6PPD-q in water samples and help identify where and when it is present in local stormwater and surface waters. The EPA is also researching the fate and transport of 6PPD-q in air and water, its ecotoxicity, its mitigation strategies, and its measurement. The EPA is developing draft screening values for 6PPD-q in water to protect salmon and other sensitive aquatic life. These values can be used by tribes, states, and other parties to evaluate monitoring results and inform water quality protection programs.
The tire industry is also researching alternative rubber preservatives to reduce dependence on 6PPD. In the meantime, continued use and development of transportation options that reduce the use of tires and roads can reduce the volume of 6PPD in the environment. For example, promoting public transit, biking, walking, carpooling, or telecommuting can reduce the number of vehicles on the road and thus the amount of tire wear and tear. Additionally, designing compact, mixed-use, and walkable communities can reduce the need for long-distance travel and sprawling infrastructure. These strategies can also reduce greenhouse gas emissions, traffic congestion, noise pollution, and urban heat island effects. But long-term planning of this type does not resolve current toxicity impacts.
What Can We Do Now to Protect Aquatic Animals?
One of the most effective ways to protect aquatic animals is to reduce the amount of stormwater runoff that carries 6PPD-q into waterways. Stormwater best management practices (BMPs) are methods that can capture, treat, or infiltrate stormwater before it reaches aquatic habitats. Some examples of stormwater BMPs are rain gardens, bioswales, permeable pavements, green roofs, rain barrels, and engineered wetlands. Stormwater BMPs can also provide other benefits such as reducing flooding, enhancing biodiversity, improving water quality, and beautifying landscapes.
Stormwater BMPs can include controlling the source of 6PPD-q through street sweeping and roof sweeping to reduce the quantity of tire particulates that accumulate. Slowing and reducing the volume of runoff using retention ponds and infiltration basins can control the flow of 6PPD-q into streams and aquatic environments. Using compost and amended soils in bioretention systems can also help capture chemicals and prevent acute mortality. Many stormwater systems may have BMPs installed, but with changes to climate and use patterns, these systems may need to be retrofitted or resized to manage runoff and reduce the likelihood of 6PPD-q reaching the environment.
What Are Federal and State Governments Doing?
The federal government held a Senate subcommittee hearing on Understanding the Potential Environmental Impacts of the Chemical 6PPD on July 31, 2024. Some states are tracking or regulating 6PPD-q in their stormwater permits or water quality standards.
- Washington State Department of Ecology has added 6PPD-q to its list of chemicals of emerging concern and has required monitoring for it in its municipal stormwater permits.
- California State Water Resources Control Board has issued a data request letter to tire manufacturers to provide information on 6PPD use and alternatives. The California Department of Toxic Substances Control began regulating 6PPD in October 2023.
- Oregon Department of Environmental Quality has initiated rulemaking to establish water quality criteria for 6PPD-q.
KJ’s Stormwater group is a good resource for additional information on 6PPD, and can answer questions about best management practices. Contact us if you have questions or concerns about your system.
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