Investigation of Toxic Chemicals in Roof Runoff
In a collaborative coalition between the Washington State Department of Ecology (Ecology), Washington State University, the Washington Stormwater Center and a Roofing Task Force (RTF) of roofing manufacturers, their associations, stormwater programs, and environmental stakeholders, toxic chemicals in the runoff from roofing materials was assessed.
The need for scientifically credible data to guide permitted jurisdictions has become increasingly important as compliance requirements strengthen and suggested BMPs are tested. Although not often highlighted, the impact from roofing runoff into surrounding water bodies is now becoming a new zone for inquiry to understand and substantiate the premise that roofing runoff is a contributor to degrading water quality. A previous study by Ecology indicated that roofing materials appeared to be major sources of copper, cadmium, zinc, arsenic, and possibly polycyclic aromatic hydrocarbons (PAHs) and phthalates in the Puget Sound basin (Ecology, 2011a and b).
During the spring of 2013 and fall/winter of 2013/2014, the coalition collected and analyzed samples of runoff from 18 specially constructed roofing panels during 20 storm events in Lacey, WA. The panels represented 14 different types of roofing material that are the most commonly installed in the Puget Sound basin, replicates of the most common roofing materials, and two glass controls. All roofs were installed at slopes typical of either residential or commercial roofing, faced the prevailing wind direction and were exposed to the same rain events. The 20 storm events sampled ranged in size from 0.05 to 0.75 inches. Analysis of the roof runoff included total metals (arsenic, cadmium, copper, lead, and zinc) and organic compounds [polycyclic aromatic hydrocarbons (PAHs), phthalates, and polybrominated diphenyl ethers(PBDEs)].
Sampling characterized the metals and organics released from new roofing materials under the climatic conditions in the Puget Sound basin. Analysis identified significantly higher concentrations of metals in runoff from several roofing types when compared to the glass controls. Most notably, concentrations of arsenic, copper, and zinc were substantially elevated in some roofing types. The new, unaged roofing materials evaluated in this study did not appear to be releasing phthalates or PBDEs to the runoff after the first sampling round. PAH concentrations released from the new roofing materials were low.
The study is intended to inform the public, municipalities, businesses and regulatory agencies on the potential for roofing materials to cause pollution.