It allowed playing fields to move indoors and greatly reduced the maintenance required for outdoor fields. In urban areas, lots could easily be covered and turned into grassy play areas for kids. There are currently more than 12,000 artificial turf fields in the U.S., and another 1500 are installed each year. But after decades of use, questions have been raised about the safety of these surfaces.

Concussion Concerns

In its early years, artificial turf was simply plastic grass with no additional cushioning, which was pretty tough on players’ bodies. In the early 2000s, artificial turf manufacturers began adding rubber “crumbs” from old tires to soften the surface, but even with additional cushioning artificial turf tends to be harder on players’ bodies than natural grass.

While it’s true that even natural grass fields can become quite hard, particularly when temperatures drop below freezing, artificial turf generally “gives” less than real grass when a player’s body hits it. And though many schools and municipalities turn to artificial turf to reduce maintenance, these surfaces must be maintained to perform properly. Professional sports teams run machines costing thousands of dollars several times per week to redistribute the rubber cushioning. High schools and municipalities tend not to invest in the equipment or staff time, in part because they chose the artificial turf to save time and money on upkeep. So artificial fields tend to be significantly harder than natural turf and put players at risk for injury.

A 1992 study from the University of Iowa was the first of many to demonstrate that athletes who played on artificial turf were more prone to anterior cruciate ligament (ACL) and other injuries and suffered more muscle soreness. Players complained about the artificial turf used in the 2015 Women’s World Cup because of the increased recovery time it required. One player brought attention to the ways artificial turf beat up her legs when she tweeted a photo of the cuts she sustained during a game. A team member commented that the surface felt like cement.

In addition to bodily injuries, artificial turf plays a significant role in the incidence of concussion among athletes. A white paper published by the Concussion Legacy Foundation titled the Role of Synthetic Turf in Concussion reports that 1 in 5 concussions in high school sports occur when players’ heads hit the field. In college sports, the figure is 1 in 10. The authors speculate that hundreds of thousands of concussions annually result from head contact with hard playing surfaces. They argue that since contact with the surface of a playing field can have such a significant effect on head injuries, that “Artificial surfaces should receive the same attention and scrutiny as football helmets.”

Additionally, artificial turf surfaces become much hotter than natural grass. One study found the temperature of the artificial turf to be 117 when natural grass registered only 78, and similar readings were taken at the 2015 Women’s World Cup. Heat stress is another serious concern for athletes playing on artificial turf.

Toxic Turf?

Perhaps even more worrying are the possible health effects of exposure to toxins in artificial playing fields. The tire crumb infill used in artificial turf contains chemical compounds from tens of thousands of different tires, including lead, benzene, and an array of other industrial chemicals and heavy metals. Athletes may be exposed to these compounds through multiple routes, including ingestion, skin contact, and inhalation when the tire crumbs are disturbed by players’ feet. Though many studies have detected what are considered safe levels of these compounds in artificial turf, they have not examined all the possible exposure routes, nor considered the effect of frequent exposure or how very low levels may affect young children, whose developing nervous systems may be more susceptible to tiny amounts of neurotoxins like lead.

Responding to concerns about the safety of recycled tires in artificial turf materials, in February of this year the U.S. Environmental Protection Agency, the Centers for Disease Control and Prevention, the Agency for Toxic Substances and Disease Registry (ATSDR), and the U.S. Consumer Product Safety Commission (CPSC) began an investigation of the safety of recycled tire material. The EPA notes that “Prior research has not definitively demonstrated a health risk from playing on artificial turf, but the EPA recognizes that the data is too limited to conclude that artificial turf poses no health risk and warrants further research.” They aim to address these shortcomings by investigating “both the chemical makeup of the tire crumbs used in playing fields and the people who have played on them for substantial amounts of time.”

Using a robot to sample the particulates released from movement on the playing surface, one 2011 study determined that even on fields where surface samples contained contaminants below accepted levels of concern, particulates released into the air above the surface when played on could be far higher. The study concluded that inhalation of lead particles was a real concern for young athletes playing on the sampled surface, especially the smallest players, who are down closer to the level where particulates become airborne. Athletes who hit the ground repeatedly will likewise inhale and ingest more particles, which can also become lodged in skin abrasions.

Amy Griffin, a soccer coach at the University of Washington, noticed a surprising number of soccer goalies diagnosed with non Hodgkins lymphoma. To date, she has compiled a list of 200 young athletes with cancer who have played on artificial turf. Ninety-five of them are soccer goalies.

Some municipalities have refused to test their fields for contaminants like lead because of the high cost of replacing them should they be found hazardous. If research into tire crumbs suggests that health risks are too great, field owners may be facing significant costs to replace them. But pretending there’s no problem because you refuse to check for one is hardly a logical way to proceed, especially because so many of these fields are meant to promote the health and wellbeing of children.

Cost-Benefit Analysis

One of the advantages of artificial turf is that it can be played on far more frequently than real grass, which wears out if used as often, so school districts and towns can get by with fewer fields, saving both money and space.

The Synthetic Turf Council points out that in addition to reducing maintenance and being impervious to weeds, artificial turf playing fields have other environmental advantages. They don’t require fertilizer or herbicides, both potent contributors of climate-changing greenhouse gases. They also save a lot of water: the Council estimates that an average playing field might drink up to a million gallons of water per season. And those tire crumbs seemed like a brilliant way to address the waste problem posed by discarded tires.

It’s the varied chemical components of tire crumbs that worry toxics researchers most, so one solution is to use other available fillers, like sand or coconut husks. In 2009 the New York City Department of Parks and Recreation and Los Angeles Unified School District banned crumb rubber in new fields. Many other cities and towns have decided against installing artificial turf playing fields altogether.

As with so many things in modern life, money- and time-saving inventions often come with serious tradeoffs, including dangerous, even life-threatening, health risks. Artificial turf might be yet another example where the tradeoffs prove too great.