Assessment of overall chemical hazard of runoff from eight roofing materials applying effect-based analysis

Urban runoff carries a variety of compounds many of which are largely unknown organic pollutants occurring in low concentrations. This study combines analyses targeting known contaminants (metals, phthalates and nonylphenols, octylphenols and their ethoxylates) with effect-based methods that indicate the mixture effects of known and unknown substances. The potential chemical hazard of roof runoff was investigated during a rain event sampled in June in Luleå, northern Sweden. The investigation included measures of oxidative stress response, aryl hydrocarbon (AhR) activation, and endocrine disruption (androgenic, antiandrogenic and estrogenic effects) of the dissolved and the particulate phases in the water. In the runoff, significant metal release from copper (5320 μg Cu/L), zinc (8690 μg Zn/L) and galvanized roofs (8050 μg Zn/L) was observed, whereas for organic compounds only DINP (280 μg/L) and DEHP (1.8 μg/L) were detected from one of the PVC roofs. Results on biological effects showed cytotoxic interference for most samples and genotoxicity for all samples. For each assay, specific effects were detected in ≥50 % of the samples except for androgenic activity. Most commonly, oxidative stress and AhR activity were observed. For oxidative stress, the range of BEQ concentrations was <14-131 μg/L tBHQeq (dissolved phase) and 9.04-50.8 μg/L tBHQeq (particulate phase). For AhR activity, the range was <0.427-5.8 ng/L TCDDeq (dissolved phase) and 0.383-23.5 ng/L TCDDeq (particulate phase). Particles accounted for a high share of activity in runoff for the AhR assay (>70 % for majority of samples), whereas for the other assays the share was more variable. Results of this study suggest that chemicals present in the roof runoff may cause biological effects that are higher compared to drinking water samples and in similar ranges to those previously reported for stormwater from larger catchments for oxidative stress and AhR activity.