Emerging contaminants in stormwater: Tire-derived chemicals, pharmaceuticals, and heavy metals detected in a United Arab Emirates extreme weather event

Climate change is associated with the intensification of weather patterns, including extreme weather events of historically arid regions such as the United Arab Emirates (UAE). On April 16–17, 2024, the UAE experienced a severe storm with unusually heavy precipitation, which resulted in widespread urban flooding, contaminated floodwaters, and the potential for cross-contamination in water distribution systems. Ten floodwater samples from around the American University of Sharjah, UAE, were analyzed for the presence of emerging contaminants (e.g., tire-derived chemicals, pharmaceuticals, and personal care products (PPCPs)) and selected metals. Tire-derived chemicals were detected at varying concentrations: N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) (<detection limit - 26 ng/L), 6PPD-quinone (20–270 ng/L), 1,3-diphenylguanidine (DPG) (490–14,340 ng/L), and hexa(methoxymethyl)melamine (HMMM) (70–15,800 ng/L). Four PPCPs (caffeine, cotinine, acetaminophen, and lidocaine) were detected at lower concentrations (42–779 ng/L, 6–179 ng/L, 4–196 ng/L, and 1–7 ng/L, respectively). Significantly higher amounts of all tire-derived chemicals and PPCPs were observed in samples from outside the campus. Metals were also detected: aluminum (92–218 µg/L), iron (49–349 µg/L), potassium (160–3860 µg/L), manganese (3 µg/L), and barium (1–7 µg/L). Correlation analysis revealed a strong positive correlation between 6PPD-quinone and HMMM (r = 0.893, p = 0.000507), and among acetaminophen, caffeine, cotinine, and lidocaine (r = 0.501–0.980, and p < 0.05), suggesting shared sources stemming from high vehicular activity and raw wastewater overflow. These findings emphasize the need for arid regions to implement targeted stormwater management and monitoring strategies during extreme weather events to address floodwater-driven mobilization of environmental contaminants.