Presence and risk assessment of herbicides in the marine environment of Camps Bay (Cape Town, South Africa).

The present study was conducted during a time of drought to assess the concentration of herbicides and their potential for accumulation in marine biota found in the near shore marine environment of an urban setting (Camps Bay, Cape Town, South Africa). The purpose was to establish whether raw sewage containing selected persistent chemicals that are released through a local marine outfall would be sufficiently diluted by the ocean to prevent impact on the near-shore marine environment of the suburb Camps Bay. Samples of seawater, sediment, seaweed, and selected marine organisms present in the near shore environment, such as limpets (Cymbula granatina), mussels (Mytilus galloprovincialis), and sea urchins (Parechinus angulosus), were analysed for five indicator herbicides, namely atrazine, alachlor, simazine, metolachlor, and butachlor, with gas chromatography coupled with a mass spectrometer. The concentration of the compounds detected ranged from below the limit of detection (<LOD) to 4.2 ng/L in seawater, <LOD to 45.3 ng/g dry weight (dw) in sediments, <LOD to 157.8 ng/g dw in marine organisms, and between 12.3 and 87.0 ng/g dw in seaweed. Results of ecological risk assessment for acute and chronic risk, calculated following the US Environmental Protection Agency method, showed a possible threat to the near shore environment from sewage released by the marine outfall, as the herbicide contamination in the biota posed a low to high ecotoxicological risk for marine organisms. The hazard quotients and carcinogenic risk caused by herbicide pollution in Camps Bay seawater were above the acceptable level indicating that these chemicals pose adverse health effects, should an average sized human (70 kg) consume any of the marine species analysed herein on a daily basis (daily consumption of 54 g), over a lifetime period (life expectancy of 70 years). The study also indicated the extensive use of these herbicides for cosmetic and ornamental purposes in gardening, or for weed control in an urban setting, thus, it is apparent that consumers and municipalities need to be educated about their inadvertent use and safe disposal of these compounds. The use of these herbicides to control weeds within the area and discharge of sewage to Camps Bay must be checked through adequate control of the trade, handling of herbicides, and enforcement of appropriate sanctions and development of suitable regulations.