Synthetic turf has become a widespread alternative to natural grass for sports fields, playgrounds, and recreational areas due to its durability and lower maintenance requirements. However, its increasing prevalence has led to public questions regarding its safety, particularly concerning a potential link to cancer. This article explores the scientific understanding of synthetic turf materials, the findings from various health assessments, potential exposure routes, and the current recommendations for safe use.
Understanding Synthetic Turf Materials
Modern synthetic turf systems consist of synthetic fibers, a backing material, and infill granules. Infill materials are the primary focus of health discussions, with crumb rubber being the most common type. Crumb rubber, produced from recycled tires, contains various chemicals, including polycyclic aromatic hydrocarbons (PAHs), heavy metals (zinc, aluminum, iron, lead), volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs). Some of these chemicals are known carcinogens or neurotoxicants. Other infill options exist, such as thermoplastic elastomers (TPE), ethylene propylene diene monomer (EPDM), and organic materials like cork or coconut fibers.
Total PAH levels in crumb rubber samples have been found to vary widely, from 0.4 mg/kg to 3196 mg/kg. Median concentrations of heavy metals like aluminum and zinc in crumb rubber infill can be as high as 5382 mg/kg and 5165 mg/kg, respectively.
Scientific Inquiry into Cancer Links
Government agencies and scientific bodies have conducted numerous studies and health assessments to investigate the potential link between synthetic turf, particularly crumb rubber infill, and cancer. The U.S. Environmental Protection Agency (EPA), in partnership with the Centers for Disease Control and Prevention (CDC) and the Consumer Product Safety Commission (CPSC), launched a Federal Research Action Plan in 2016 to investigate potential human health implications from tire crumb rubber. These agencies noted that earlier findings on crumb rubber safety were based on “limited” studies and did not comprehensively evaluate health risks.
This plan aimed to characterize chemicals in tire crumb rubber and understand potential human exposures. While these findings inform future risk assessments, they do not directly assess risks associated with playing on synthetic turf fields.
Despite ongoing investigations, most comprehensive reviews and epidemiological studies to date have not found a direct, causal link between synthetic turf exposure and an increased risk of cancer based on available evidence. For example, a 2017 investigation by the Washington State Department of Health found no significant association between artificial turf exposure and cancer incidences among skilled female college soccer players compared to other residents of the state. Similarly, an investigation into the association between turf field density and cancer incidences in California counties also found no significant link.
Challenges in conducting long-term epidemiological studies include the difficulty in isolating turf-specific exposures from other environmental factors and the extended latency period for many cancers. Some human health risk assessments (HHRAs) have identified potential cancer risks from PAH ingestion in children with pica, and heavy metal exposure. However, definitive conclusions on human health risks under real-world scenarios remain elusive. Some studies suggest that certain PAH and metal exposures from synthetic turf may be similar to or lower than typical background exposures.
Pathways of Exposure
Individuals using synthetic turf fields, particularly athletes and young children, can be exposed to chemicals present in the infill through several pathways. One common route is inhalation, where users may breathe in dust particles or volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) released from the crumb rubber, especially under hot conditions. Air monitoring studies have shown varying levels of VOCs, with higher concentrations observed in warmer months.
Another pathway is incidental ingestion, which occurs when small crumb rubber particles are unintentionally swallowed. This is of particular concern for young children who may put objects in their mouths or play directly on the turf. Dermal contact, or skin exposure, is also possible, especially through cuts, abrasions, or when crumb rubber adheres to skin and clothing.
While exposure to these chemicals can occur, the key factor in determining health risk is the dose and the toxicity of the specific compounds. Studies have found that while chemicals like PAHs and heavy metals exist in infill, their bioaccessibility—how much of a substance is absorbed into the body—can vary. For example, PAHs generally show low bioaccessibility, while some heavy metals are more bioaccessible.
Current Safety Guidelines and Precautions
Given the ongoing research and public interest, health authorities and sports organizations often provide general advice and recommendations for the safe use of synthetic turf fields. One common recommendation is to ensure proper ventilation in indoor facilities to prevent the buildup of VOCs and SVOCs. Adequate air circulation can help disperse any released chemicals.
Practical precautions individuals can take after using synthetic turf fields include:
- Washing hands thoroughly and showering to remove any residual crumb rubber particles or dust from the skin and hair.
- Avoiding ingesting infill particles.
- Supervising young children to prevent them from putting crumb rubber in their mouths.
- Cleaning the turf regularly to remove debris and reduce exposure to accumulated substances.
Field owners and facility managers are encouraged to maintain fields according to manufacturer guidelines and consider heat mitigation features, as synthetic turf can become very hot, especially in direct sunlight. These precautions aim to minimize potential exposures and address public concerns regarding synthetic turf use.