Tire Crumb Questions and Answers

• Which agencies are involved with the Federal Research Action Plan?
• What research is included in the Federal Research Action Plan? Will it answer the question of whether tire crumb rubber is safe?
• Where are the fields located that will be studied?
• What are the key findings of the Literature Review/Gaps Analysis?
• Who regulates the management and disposal of used tires?
• How is tire crumb rubber produced?
• Are the results of this federal research publicly available?
• Why did the Agency not conduct a complete risk assessment?
• States and other organizations have conducted studies on tire crumb rubber. What have they concluded? How is the Federal Government working with California?
• What advice do you have for communities who are concerned about the use of tire crumb rubber in fields?
• How is the federal study similar to and different from other research studies?
• What important data gaps is the federal study filling?
• What is the status of CPSC’s review of playgrounds with tire crumb rubber?
• Do tire crumbs contain PFAS? If yes, were exposures to PFAS characterized?
• Did this study consider exposures to 6-PPD quinone?
• Why do PAHs increase after exercise?
• Does EPA have guidance about how to handle the disposal of turf fields and concerns related to the disposal of these fields?

This plan was led and primarily implemented by the US Environmental Protection Agency (EPA) and the Centers for Disease Control and Prevention’s Agency for Toxic Substances and Disease Registry (CDC/ATSDR), in cooperation with the US Consumer Product Safety Commission (CPSC) and other agencies. Other agencies such as National Institute of Environmental Health Sciences, the U.S. Department of Defense and California’s Office of Environmental Health Hazard Assessment (OEHHA) are provided expertise, facilities, and/or sharing of information.

Q. What research is included in the Federal Research Action Plan? Will it answer the question of whether tire crumb rubber is safe?

The plan included four research activities:

1. Outreach to key stakeholders - EPA, CDC/ATSDR, and CPSC had discussions with other government agencies that have researched or are currently researching tire crumb rubber and other key stakeholder groups including tire crumb rubber manufacturers, non-profit organizations, field installers and maintenance professionals, and field users to provide expertise to inform the federal study.
2. Analysis of data gaps - EPA, CDC/ATSDR, and CPSC evaluated the existing scientific information related to the use of tire crumb rubber in synthetic turf fields to understand the current state-of-the-science and inform the research activities. The Literature Review and Data Gaps Analysis is included in the status report released in December 2016. 
3. Characterization of the chemicals found in tire crumb rubber - EPA and CDC/ATSDR tested tire crumb rubber from different tire recycling facilities and fields. These tests, along with existing scientific information from the literature, will help us better understand the make-up of tire crumb rubber. The Part 1 Report on Tire Crumb Rubber Characterization is now available and can be viewed here. 
4. Characterization of the exposure scenarios - EPA and CDC/ATSDR conducted several activities to better understand potential exposures that may occur when people use synthetic turf fields. This work considered all possible ways that one may be exposed including by breathing, unintentionally ingesting, or touching tire crumb rubber or the chemicals in tire crumb rubber. The report is now available and can be viewed here.

Study research activities were prioritized based on data needs and available resources. While this effort doesn't provide all the answers related to this topic, the study will provide a better understanding of the chemicals found in tire crumb rubber and the potential exposures that field users may experience by using these fields. This study is not a risk assessment, however, the results of the research described in this, and future reports will advance our understanding of exposure to inform the risk assessment process.

For more information about the study and timeline, see our website on the Federal Research on Recycled Tire Crumb Used on Playing Fields.

Q: Where are the fields located that will be studied in the tire crumb rubber characterization and exposure study?

Tire crumb rubber samples were collected from 40 different playing fields within the four US census regions. These locations include both outdoor and indoor playing fields. The exposure pilot study and the supplemental biomonitoring study were conducted at three of these 40 fields. Samples were also collected from nine tire recycling facilities. To protect privacy, the names of the specific locations sampled will not be released to the public.

Q. What are the key findings of the Literature Review/Gaps Analysis?

An important component of any research is to understand the state of the science and any data gaps. The Literature Review and Data Gaps Analysis (LRGA) provides a current summary of the available literature and capture the data gaps as characterized in those publications. The overall goals of the LRGA were to inform the interagency research study and to identify potential areas for future research that might be needed. The LRGA does not include critical reviews of the strengths and weaknesses of each study but does provide the author’s conclusions regarding their research, where applicable. The LRGA also does not make any conclusions or recommendations regarding the safety of the use of tire crumb rubber in synthetic turf fields and playgrounds. The LRGA identified 90 references. Each reference reviewed was categorized according to 20 general information categories (e.g., study topic, geographic location, sample type, conditions, and populations studied) and more than 100 sub-categories (e.g., study topic subcategories: site characterization, production process, leaching, off-gassing, microbial analysis, and human risk). The research in the FRAP addresses many of the gaps identified in the LRGA, particularly with respect to tire crumb rubber characterization and exposure characterization. The review provides information useful for guiding and designing future research efforts needed to further address questions regarding exposures and risks for tire crumb rubber used in synthetic turf fields and playgrounds.

Q. Who regulates the management and disposal of used tires?

State solid waste agencies are primarily responsible for regulating the management of used tires at their end of life, including options for recycling and disposal. You can consult your state solid waste regulatory agency for information and guidance on the proper management of used tires in a particular state.  

Q. How is tire crumb rubber produced?

Tire crumb rubber is manufactured by reducing scrap tires down to various sizes depending on its intended application and market use, and by removing 99 percent or more of the steel and fabric from them. The tire crumb is classified by sifting screens that return oversize pieces back into the reduction process. Magnets are used throughout the process to remove the wire and other metal contaminants and air separators are used to remove the fabric. The American Society for Testing Materials (ASTM) has a standard test method (ASTM D5644) for determining the particle size distribution of vulcanized particulate rubber (a.k.a. tire crumb rubber). ASTM D5603 classifies vulcanized particulate rubber based on particle size distribution and origin of the rubber.

Q. Are the results of this federal research publicly available?  

This work was reported and released in four parts, all are now completed and available.

Q. Why did the Agency not conduct a complete risk assessment?

In 2016, the EPA recognized that without exposure there is no risk and to develop a timely response to ongoing concerns identified gaps in its knowledge about the potential exposures to the chemicals contained in tire crumb rubber. After consultation with the Obama Administration, EPA, CDC/ATSDR, and CPSC launched this coordinated federal effort to fill important data gaps particularly with respect to understanding potential exposures to chemicals in tire crumb rubber. This research can inform future risks assessments.

Q. States and other organizations have conducted studies on tire crumb rubber. What have they concluded? How is the Federal Government working with California?

The Washington State Department of Health (DOH), in collaboration with the University of Washington School of Public Health conducted an investigation of reported cancer among soccer players, which can be viewed here.

California’s Office of Environmental Health Hazard Assessment (OEHHA), under contract from CalRecycle, is conducting an evaluation of tire crumb rubber. That can be viewed here. EPA and OEHHA have been sharing information on their respective studies through a Materials Cooperative Research and Development Agreement.

Several organizations have published important information on this topic since the FRAP literature review and data gaps analysis was completed and published in December 2016. Brief summaries of some of these research efforts and publications have been included in the Part 1 report.

Q. What advice do you have for communities who are concerned about the use of tire crumb rubber in fields?

Concerned individuals and community members  are encouraged to explore the federal agencies’ websites (CPSC and EPA) to review the research results available to date on the use of tire crumb rubber in playgrounds and synthetic turf fields. In addition, concerned individuals can check their state’s public health agency websites to determine if there are state-specific recommendations. EPA has compiled a list of information sources from state government websites, which can be found here.

Q. How is the federal study similar to and different from other research studies?

The study shares similarities with ongoing and recent studies like those conducted by Cal-OEHHA, National Toxicology Program, National Institute for Public Health and the Environment (RIVM), and European Chemicals Agency, but also has important differences. Together, these studies provide a range of information that is complementary, while significantly increasing our knowledge about the physical and chemical properties of tire crumb rubber, how people are exposed to these chemicals, and whether there may be health concerns related to the use of tire crumb rubber. For example, NTP provided some additional information about the chemicals that may be associated with tire crumb rubber, which aligns and compliments with findings gained from the EPA and CDC/ATSDR tire crumb rubber research activities. NTP has also provided research results from short-term in-vivo and in-vitro toxicity tests.

The federal study characterized tire crumb rubber from recycling plants, indoor, and outdoor fields across the United States, while Cal-OEHHA focuses on outdoor fields in California and RIVM studied outdoor fields in the Netherlands. Many of the same metal and organic chemicals are being measured in the studies, with some differences in measured chemicals across the studies that will broaden our understanding of the chemical landscape. Altogether, approximately 175 fields are included across the three studies, improving our understanding about the range and variability of chemicals associated with tire crumb rubber. The federal study includes indoor fields while the other studies do not. All three studies examined the bioaccessibility of some chemicals.

While multiple studies are applying exposure modeling approaches, the federal study also assessed the availability and suitability of measurement data and exposure parameter information for exposure modeling.

Q. What important data gaps is the federal study filling?

Previous studies in the United States that assessed chemicals in tire crumb rubber have been based on samples collected only from a few fields and measured only a limited number of chemicals. The federal study:

• Systematically measured a wide range of physical, chemical, and microbial characteristics, and assessed the variability of these characteristics across several recycling plants and a number of fields.
• Measured important exposure-related characteristics including emissions and bioaccessibility. 
• Assessed the human activity parameters that affect exposures, developed and applied exposure measurement methods for children and adults, applied biomonitoring measurements, and assessed human exposure modeling approaches.

The Federal study helps fill important knowledge gaps for tire crumb rubber characterization and provides a better understanding of how people using synthetic turf fields may be exposed to chemicals associated with tire crumb rubber.

Q. What is the status of CPSC’s review of playgrounds with crumb rubber?

As part of the Federal Research Action Plan (FRAP), CPSC conducted a playground use survey gathering information about children’s behavior on playgrounds. This survey has been completed and is currently being reviewed by CPSC staff. It was released in 2019.  CPSC will continue its work on playgrounds by conducting a risk assessment of children’s exposure to playground surfaces made of tire rubber. This work will use the CPSC survey as well as data from EPA’s FRAP Part 1 (characterization of the chemicals and materials in tire rubber crumb), released July 2019, and CDC’s (ATSDR) FRAP Part 2 (characterization of potential exposures for those who use turf fields containing tire crumb rubber) released April 2024.

Q. Do tire crumbs contain PFAS?  If yes, were exposures to PFAS characterized? 
The tire crumb study did not specifically test for the presence of any PFAS target analytes.  No PFAS chemical was identified in the non-targeted analyses of tire crumb rubber.  No additional PFAS characterization of rubber or other turf components is planned. 

Q. Did this study consider exposures to 6-PPD quinone? 
6-PPD is a component of automotive tires that prevents them from breaking down, helping them last longer. When 6PPD is exposed to air, it reacts with ozone to create 6PPD-quinone. Neither 6PPD nor 6PPD-quinone were target analytes in the FRAP research study. 6PPD was included as a suspect screening compound in the study and was tentatively identified in tire crumb rubber samples from tire recycling plants and in tire crumb rubber infill samples. At the time the study was conducted, 6PPD-quinone had not been previously reported or identified as a chemical of potential interest. With the techniques used, no chemical with the 6PPD-quinone formula was identified in the non-targeted analyses.

Q. Why do PAHs increase after exercise?   
Though some statistical models indicated a difference in pre- and post-activity PAH concentrations, these observed differences were not explained by field type.  The observed differences could be due to factors no captured in the study, such as changes in hydration level through sweating.  Overall, pre- and post-activity differences in urinary PAH concentrations were similar for synthetic turf field users and natural grass field users.  

Q. Does EPA have guidance about how to handle the disposal of turf fields and concerns related to the disposal of these fields?
 Landfills that accept municipal solid waste (MSW) are primarily regulated by state, tribal, and local governments. Information about MSW landfill requirements are best addressed by those same entities.