A recent study by US Geological Survey shows a broad range of chemicals are found in low concentrations downstream from urban areas. The waterways are contaminated with traces of chemicals such as caffeine, contraceptives, painkillers, insect repellent, perfumes, nicotine, beauty aids and cleaners. Researchers warn that these substances do not disappear. US Geological Survey tested water samples from urban area streams for three years in 30 states for 95 pharmaceutical and personal care pollutants. The use and disposal of 81 of the 95 compounds are unregulated and often escape wastewater treatment. The potential health and environmental effect are unknown. Scientists suspect the use of anti-bacterial agents in household cleaners and human and veterinary medicines encourage the development of germs that are resistant to antibiotics. Reproductive hormones from contraceptives have the most serious implications for the health of aquatic organisms since even low exposure to hormones can cause negative biological impacts.