Ecological risk assessment of pesticide runoff from grass surfaces

An ecological risk assessment was performed for runoff of 37 pesticides registered for use on grass surfaces (lawns and golf courses) in the U.S. The assessment was based on 100-yr simulations using TPQPond, a newly developed model of pesticide runoff and subsequent accumulation in a receiving pond. One-in-10 yr pond concentrations were compared with acute toxicity end points for fish, invertebrates, and algae. Simulations were performed for pesticides applied at label rates on lawns, fairways, and greens using weather data for nine U.S. locations. Runoff of 4 of the 37 pesticides produced potential acute risk to invertebrates or fish. Two chemicals posed a comparable danger to plants. Risk was highest with fairways and lowest for greens. Locations with long growing seasons and large amounts of precipitation produced the highest risks. The risk assessment followed the general protocols recommended by USEPA, but with different models, weather data, and scenarios. In spite of the differences, the results confirmed that most but not all of the pesticides which had survived the USEPA registration process were also demonstrated safe, with respect to acute risks, by this independent assessment. The five exceptions were explained by differences in models, simulation scenarios, and input data. These results do not mean that the studied pesticides are free of any ecological dangers. In particular, no attempt was made to evaluate chronic risk.