The widespread use of synthetic turf fields offers durability and reduced maintenance compared to natural grass. This material is a fixture in many communities, serving as a reliable surface for sports and recreation. However, the materials used to create these fields have generated public health concerns regarding a potential link between exposure and long-term health risks, particularly cancer. This controversy has prompted a closer look at the components of the turf system and the scientific evidence surrounding its safety. This analysis explores the composition of synthetic turf and the current state of research addressing this public health concern.
Composition of Synthetic Turf Infill
The material at the center of health concerns is the infill, which consists of tiny black granules known as crumb rubber. This infill is derived from pulverized, end-of-life vehicle tires, creating the shock-absorbing layer between the synthetic grass blades. Crumb rubber contains a variety of organic and inorganic compounds originally incorporated into the tires.
Among the most concerning substances are Polycyclic Aromatic Hydrocarbons (PAHs), a class of chemicals formed during the burning of organic material. Studies have detected PAHs in crumb rubber infill at widely varying concentrations. Specific PAHs identified include benzo[a]pyrene and chrysene, which are known or probable human carcinogens.
The infill also contains various heavy metals incorporated during tire manufacturing. Zinc is frequently found in high concentrations. Lead and chromium are also present, though typically at lower levels, and are substances of concern due to their known toxicity. Additionally, the infill can release Volatile Organic Compounds (VOCs) and semi-volatile organic compounds (SVOCs), such as benzene and methylene chloride, which off-gas from the rubber material into the air.
Mechanisms of Chemical Exposure
Chemicals embedded within the crumb rubber infill can enter the human body through three primary pathways during turf use.
The first is inhalation, where users breathe in dust particles or volatile gases released by the infill. High temperatures on the field often exacerbate the off-gassing of VOCs and SVOCs, increasing their release into the breathing zone.
The second route is incidental ingestion of the small rubber particles. This is a concern for younger children who may put contaminated hands or objects into their mouths.
The third pathway involves dermal contact, where chemicals can be absorbed through the skin. Abrasions from sliding or falling, commonly known as “turf burns,” create open wounds that may allow direct contact and absorption of chemical constituents.
Scientific Research and Health Findings
The question of whether exposure to synthetic turf infill causes cancer has driven numerous investigations, yet a definitive causal link remains elusive. Early public concern was spurred by anecdotal reports, such as a cluster of cancer cases among female soccer players. However, epidemiological studies designed to find a statistical association between synthetic turf use and cancer incidence have been inconclusive or limited.
Two epidemiological studies specifically investigated the link between synthetic turf exposure and the incidence of leukemia, non-Hodgkin lymphoma, and Hodgkin lymphoma, finding no significant association. A statistical analysis of cancer rates among soccer players in Washington State found that the incidence rate was not higher than that of the general population. These findings highlight the difficulty in establishing a direct cause-and-effect relationship in a large population, given the many confounding factors in cancer development.
While a direct human epidemiological link has not been established, toxicological studies confirm the presence of hazardous substances. The California Office of Environmental Health Assessment (OEHHA) conducted simulations showing that known carcinogens like chrysene were found in samples at levels above established safety standards. This confirms the chemicals are present, but the question remains whether the level of human exposure during typical use is high enough to translate into an elevated health risk.
In response to the uncertainty, the U.S. Environmental Protection Agency (EPA), the Centers for Disease Control and Prevention (CDC), and the Consumer Product Safety Commission (CPSC) launched a Federal Research Action Plan in 2016. The goal of this multi-agency effort is to characterize the chemicals present in crumb rubber and better understand the potential for human exposure. This research provides data on the material and exposure pathways, which informs future risk assessments, but it does not constitute a final risk assessment on the safety of the fields.
Regulatory Responses and Safer Alternatives
Regulatory bodies have responded to public concern by initiating comprehensive risk assessments and policy development. The Federal Research Action Plan aims to fill data gaps regarding chemical characterization and exposure potential. While federal agencies focus on research, some regional authorities, such as the European Union, have limited the concentration of specific hazardous chemicals in infill materials.
A variety of alternatives to crumb rubber infill have emerged and are being adopted in new installations. Organic infills provide a natural option, utilizing materials such as coconut fiber, cork, or processed nutshells. These plant-based options avoid the chemical composition inherent to recycled tires.
Synthetic alternatives have also been developed to provide durable, non-toxic infill material. These include thermoplastic elastomers (TPE) and ethylene propylene diene monomer (EPDM), which are synthetic rubbers manufactured to be free of the hazardous chemicals found in recycled tires. These alternatives maintain the performance and low maintenance of synthetic turf while addressing the chemical concerns associated with traditional crumb rubber infill.