An investigation of surface temperatures and measures of heat stress at two synthetic turf fields in Environmental Justice Communities in New York City

Background:

In the summer of 2008, the New York State Department of Environmental Conservation (NYSDEC) investigated surface temperatures and measures of heat stress at two synthetic turf fields Thomas Jefferson and John Mullaly parks in New York City (NYC). Both fields were constructed using crumb rubber which is finely ground rubber derived from recycled or scrap tires and is a common infill material for synthetic turf fields providing cushion and ballast for the playing surface. Many studies have reported occasions of high surface temperatures on these types of fields and have raised concern about potential heat stress to users.

The two fields evaluated in this investigation were located in environmental justice areas (EJ) in NYC. NYSDEC defines potential EJ areas based on the percentage of minority or low-income populations. Seventy percent of the State's EJ areas are located in NYC. A recently released study found the rate of severe obesity among U.S. children and teenagers highest among African-Americans and Mexican-Americans as compared to their white peers and higher among lower-income children as compared to higher-income families. This study highlights the importance of access to safe areas for play and exercise for minority and low income populations.

Synthetic turf fields are used by many park agencies and school districts because they provide a durable, nearly year-round playing surface which is even and consistent leading to fewer injuries compared to natural grass. The NYC area with limited open space and high population density has 94 of the State's 150 synthetic turf fields.

Objective:

Conduct a temperature survey to gain a better understanding of the surface temperature of synthetic turf fields and the potential for field users to suffer from heat-related illness (heat stress).

Methods:

Surface temperatures were measured using an infrared thermometer (DeltaTrak Thermo Trace, Model #15006). The surface temperature measurements were compared to a guideline value of 120°F issued by Brigham Young University (BYU) for conducting athletic activities on synthetic turf fields.

The potential for heat stress was assessed by measuring the wet bulb globe temperature (WBGT) and heat index (HI) using a thermal environmental and heat stress monitor (Quest Technologies QUESTemp°36). WBGT measurements were compared to the American Academy of Pediatrics (AAP) policy statement addressing heat stress and exercising children and adolescents based on this index. The HI was compared with guidelines issued by the National Weather Service (NWS).

All measurements were collected between noon and 2:00 PM at a three foot height above several locations on the synthetic turf fields and comparison areas of nearby grass and sand surfaces. Measurements were obtained during the months of August and September 2008.

Results:

Thomas Jefferson Park

At least one location on the synthetic turf field was above the 120°F guideline for 12 out of 17 dates of measurements (70%), while the comparison areas never exceeded 110°F. The average synthetic turf surface was 42°F and 40°F higher than the grass and sand surface temperatures, respectively.

WBGT measurements for the synthetic turf field, grass and sand approximated log-normal distributions, and all with the same geometric mean temperature of 76°F. Use of the AAP guidelines could have led to the recommendation of some activity limitation on one or more of the surfaces for 12 of the 17 days of measurements.

Following guidelines issued by the NWS, approximately 56% of the HI values (across all measurement locations) were above 80°F and the NWS warns that fatigue is possible with prolonged exposure and/or physical activities. There was little difference in the HI measurements between the synthetic turf and comparison areas.

John Mullaly Park

Nine out of 17 dates of measurements (53%) had at least one location on the synthetic turf field above 120°F. The average synthetic turf surface was 26°F and 35°F higher than the grass and sand surface temperatures, respectively.

WBGT measurements for the synthetic turf field, grass and sand approximated log-normal distributions, and all with geometric mean temperature of 75°F. Use of the AAP guidelines could have led to the recommendation for some activity limitation on one or more surfaces for 10 of the 17 days of measurements.

Following guidelines issued by the NWS, approximately 65% of the HI values (across all measurement locations) are above 80°F and the NWS warns that fatigue is possible with prolonged exposure and/or physical activities. There was little difference in the HI measurements between the synthetic turf and comparison areas.

Conclusions:

Although little difference was found for the WBGT levels across the different surface types, however, on any given day; a small difference in WBGT could result in different guidance for the different surface types under the AAP guidelines. This study also found that the calculated heat indices exceeded the level at which the NWS issues advice regarding the potential for heat stress.

Additionally, little difference between heat stress indicator measurements for the synthetic turf, grass, and sand were found, but the surface temperatures recorded were much higher for the synthetic turf suggesting a greater potential for heat stress might exist since the body could be in prolonged contact with a surface of elevated temperature. Finally, high metabolic activity generated during active play, in addition to the heat input from the surfaces, could produce a situation leading to greater potential for heat stress on these surfaces.

Since these types of surfaces are durable and preferred in areas of high use, an outreach plan should be developed to make the public aware of potential heat-related illness at synthetic turf recreational areas. Guidance material should be sensitive to the diverse population in NYC and it should emphasize the importance of exercise and play for minority communities. A long-range strategy should be considered by the New York City Department of Parks and Recreation to include misting stations, water-based play areas and the use of infill material which does not retain heat given the projected increase in summer temperatures reported by researchers due to climate change.