In this month’s Environmental Building News, Paula Melton takes a deep look into the issue of recycled tires used in resilient flooring. She expands upon several issues, such as the use and presence of additives like benzothiazole, that we touched upon a few years ago in the Healthy Building Network (HBN) report, Avoiding Contaminants in Tire-Derived Flooring.
We expect her findings will spark further industry improvements, as apparently happened after we released our review in 2013. “Ecore, a major manufacturer of tire-derived flooring, says it has 'adopted and implemented the recommendations from the HBN study,’" Melton reported.
Before our report on tire-derived flooring, the industry’s best practice was to conduct testing for selected toxic substances, like lead, once every year or so; now, Ecore tells EBN that it is testing daily.
While this is a dramatic improvement, it is important to consider whether this is enough. Ecore says it is using the European Chemical Safety for Toys standard, EN 71-3:2013, to guide its testing. This standard allows, at most, 160 parts per million (ppm) lead in some products. It allows far less lead than the US Environmental Protection Agency currently considers to be acceptable – 400 ppm – in bare soil. But it is not quite as protective as some other standards. Few standards are as permissive as the EPA’s for lead in materials used in products that may be ingested by children. Industry and state standards for lead in materials like cullet used in fiberglass insulation, contaminated soils that are treated and reused, and fly ash used in products like wallboard, are all more restrictive than EPA’s standard.
California recently restricted lead in “manufactured soil” (which includes products like rubber mulch used in playgrounds) to 80 ppm. That’s five times more restrictive than EPA’s standard. It is based on computer modeling determined to be more protective of children’s health. In the California scenario, a toddler “plays on bare soil, exhibits hand-to-mouth behavior, and therefore ingests higher-than-average amounts of soil.” The amount of soil predicted to be ingested is small - just 100 milligrams, or 0.004 ounces each day. If the ingested soil contains 77 parts per million lead, according to their model, the child’s blood lead levels will rise by one microgram per deciliter (μg/dL). According to California, “one μg/dL is the estimated incremental increase in the blood lead level in children that would reduce intelligence quotient (IQ) by up to one point.”
Lead contamination of recycled tire rubber at levels above the 80 ppm threshold established by California is more widespread than generally understood. Ground rubber, crumb rubber, and rubber “mulch” from recycled tires are used in flooring, pavers, playgrounds, and athletic field fill. In 2008, laboratory testing found very high levels of lead in crumb rubber used to fill a synthetic soccer field at Thomas Jefferson Park in East Harlem, Manhattan. In three Thomas Jefferson Park samples, lead was present above 1,000 ppm, or 0.1% by weight: 1,158, 1,855, and 1,956 ppm. The city replaced the crumb rubber fill, and commissioned testing for every other park in the city that used recycled tires as infill, 99 fields and 15 play areas in all. Although the contracted firm typically took just one sample of fill per field, its lab results identified 15 athletic fields contaminated by lead at levels exceeding California’s 80 ppm standard. In other words, at least one in ten athletic fields using crumb rubber had levels of lead that, if ingested by young children, could permanently damage their intelligence.
When it comes to flooring, where young children crawl and put their hands in their mouths, lead content matters. Manufacturers often state that that in cured materials, like crumb rubber, toxic constituents will not be released from the vulcanized matrix at normal room temperature. Melton’s article repeats this refrain. Experts told her that “the likelihood of exposure to non-volatile compounds ought to be very low once crumb rubber is bound in a polymer matrix.” But a study conducted by Rachel Simon of the University of California, Berkeley, Laboratory for Manufacturing and Sustainability found, “Some compounds within the material will, over time, come to be released from the material and to enter the air.” UV degradation, cleaning chemicals, abrasion from use and scrubbing, and aging are just some of the ways toxic substances, even non-volatiles like lead, leave the matrix.
We’ve seen the phrase – “bound in a matrix” – uttered, then disproven, time and again. Vested interests have used the phrase to justify the use of phthalates in vinyl flooring, PCBs, lead, and nanomaterials in paint, and lead stabilizers in polyvinyl chloride pipe. Some in industry even used to say that lead used as a stabilizer in vinyl window shades was harmless, until public health officials determined that children were suffering lead poisoning after the miniblinds aged and degraded.
Our research on tire-derived flooring was one of HBN’s first investigations of contaminants in recycled materials used in building products; subsequently, we have evaluated many others. During this research, we have contacted leading recycled content processors and users. We have found some laggards in the industries, for sure, but also innovators like Ecore that break from the pack. There are many forward-thinking processors that work to deliver the highest quality feedstocks to manufacturers, and manufacturers that specify only the cleanest recycled contents.
Industry leaders are working to optimize recycling just as global resource depletion exceeds critical levels. As humanity’s consumption accelerates, both per capita and en masse, the use of recycled materials is not only preferable; scarcity will make recovering valuable material from waste an absolute necessity. It’s best to get it right as soon as possible, and to keep the lead away from children.
Thanks to Susan Sabella, Rebecca Stamm, and Peter Sullivan for their assistance with this article.
 “European Chemical Safety For Toys.” UL, 2013. http://www.ul.com/global/documents/verificationservices/businesssegments/Consumer/English/EU_A4_ChemicalSafety_Toys_SellSheet_07052013_Web.pdf.
 “Revised California Human Health Screening Level for Lead (Review Draft).” California Office of Environmental Health Hazard Assessment (OEHHA), May 14, 2009. http://oehha.ca.gov/risk/pdf/LeadCHHSL51809.pdf.
 “Preliminary Endangerment Assessment Guidance Manual.” California EPA Department of Toxic Substances Control, October 2015. https://www.dtsc.ca.gov/PublicationsForms/upload/PEA_Guidance_Manual.pdf.
 Long Island Analytical Laboratories. Memorandum. “Re: Al Oerter Recreation Center (North).” Memorandum, January 12, 2009. http://www.nycgovparks.org/sub_things_to_do/facilities/Turf_Binder_CrumbRubber.pdf.
 Melton writes, “The HBN report raises concerns about aromatic process oils, lead, and carbon black nanoparticles. Although there’s no evidence that any of these substances are released from flooring, ‘abrasion during any floor’s service life routinely releases top layer ingredients as particulates,’ creating pathways of potential exposure that haven’t been looked into by the industry, the report claims. Many experts we spoke with did not share these specific concerns, stating that the likelihood of exposure to non-volatile compounds ought to be very low once crumb rubber is bound in a polymer matrix.” Melton, Paula. “Rubber Flooring: A Good Use For Old Car Tires?” Environmental Building News, February 9, 2016. https://www2.buildinggreen.com/article/rubber-flooring-good-use-old-car-tires .
 Simon, Rachel. “Review of the Impacts of Crumb Rubber in Artificial Turf Applications.” The Corporation for Manufacturing Excellence (Manex), February 2010. http://www.libertytire.com/Libraries/Documents/UC-Berkeley-Manex-Review-of-Impacts-of-Crumb-Rubber-in-Turf.sflb.ashx .
 “… phthalates do not easily migrate out of flexible vinyl products because they have very low volatility and are tightly bound in the molecular matrix of flexible vinyl…,” claims the American Chemistry Council. (“Asthma.” American Chemistry Council. Accessed February 9, 2016. https://phthalates.americanchemistry.com/Research-Phthalates/Asthma.)
 Grossman, Elizabeth. "Nonlegacy PCBs: pigment manufacturing by-products get a second look." Environmental Health Perspectives 121, no. 3 (2013): A87-A93. https://www.pharosproject.net/uploads/files/cml/1362172506.pdf;
Kougoulis, Jiannis S., Renata Kaps, Nicholas Dodd, and Ben Walsh. Revision of EU European Ecolabel for Indoor and Outdoor Paints and Varnishes. EU Ecolabel Criteria Proposal. Technical Report. JRC European Commission. February 2013. http://susproc.jrc.ec.europa.eu/paints/docs/250213_Ecolabel%20Paints%20Technical%20report.pdf;
“Product Safety Summary: R-M® Color Bases with Lead Chromates-Lead Sulfates.” BASF, February 16, 2010. https://www.basf.com/documents/us/en/sustianability/responsible-care/R-MColorBaseswithLeadChromates-LeadSulfatesProductSafetySummary.pdf .
 "Lead stabilisers are very well bound in the PVC matrix, which is proven by a lot of migration data e.g. from potable water pipes. Lead stabilisers are not a source of significant lead emissions to the environment in their manufacture, use or subsequent disposal. The safe use of lead additives for plastics was stated in several reports," claimed the Italian PVC industry in 2000. (Vidotto, Graziano. “Answers and Comments of Graziano Vidotto on the ‘Green Book on PVC,’” July 26, 2000. http://ec.europa.eu/environment/waste/pvc/pdf/en.pdf .)
 Brown, Patricia L. "Imported blinds pose lead risk to children." New York Times (June 27, 1996). http://www.nytimes.com/1996/06/27/garden/imported-blinds-pose-lead-risk-to-children.html