Health Stream Literature Summary - Issue 50 - June 2008

Do cytotoxic chemotherapy drugs discharged into rivers pose a risk to the environment and human health? An overview and UK case study.
Johnson, A.C., Jurgens, M.D., Williams, R.J., Kummerer, K., Kortenkamp, A. and Sumpter, J.P. (2008) Journal of Hydrology, 348(1-2); 167-175.

This paper presents a preliminary risk assessment on the discharge of cytotoxic drugs (used for cancer treatment) via sewage treatment plants to water courses in the UK. The UK is particularly at risk of exposure, especially around urbanised catchments in central England which are densely populated with small rivers providing limited dilution. Over 50 cytotoxic drugs are used routinely for chemotherapy in developed countries, and the demand for chemotherapy treatment continues to increase at around 10% per year. The majority of cytotoxic drugs are highly water soluble.

A water quality model was developed for 5-fluorouracil (5FU) and its pro-drug capecitabine (metabolised to 5FU in the body) in order to assess the likely sewage effluent concentrations in the UK. 5FU is probably the cytotoxic drug used in the highest quantities in the UK. Health and Safety Executive (HSE) data for 2003 suggests that approximately 1 tonne of 5FU and 1.7 tonnes of capecitabine is used per annum in the UK, giving a combined value of 2.7 tonnes/pa. From a UK population of around 59 million people in 2003, a typical consumption value of 5FU of 125 micro g/day/head was calculated. An excretion value of 10% was assumed and no losses during sewage treatment. A 200L/head dilution in the STP was assumed and a further tenfold dilution in the river. Predicted effluent concentration for 5FU and capecitabine combined was 62 ng/L as 5FU. The GREAT-ER model was used with the 125 microg/d/head input load to predict concentrations of 5FU in the Aire and Calder catchment in North Yorkshire (UK). This model estimates the distribution of chemicals in surface waters. Using the STP loading model described above and assuming no removal in sewage treatment or in the river, river water concentrations in the urbanised reaches of this catchment were predicted to contain 5-50 ng/L of 5FU during low flow, 90th percentile conditions. Currently there is little information on the effectiveness of drinking water treatment processes to remove these compounds.

Cytotoxic drugs will probably cause the same types of genetic damage in fish and invertebrates that they do in mammals. However the concentrations that will cause significant effects is still unclear. There may be an additive effect of a mixture of low concentrations of cytotoxic drugs which needs to be considered. In terms of human exposure, the authors estimate that daily intake of 5FU from drinking water would be at least 100 million-fold lower than a therapeutic dose, or at least 300 times lower than a precautionary threshold of toxicological concern. Further research is required with particular focus on predicted no effect concentrations for freshwater aquatic organisms; measurements to identify water concentrations of a range of relevant cytotoxic drugs in receiving water and where appropriate drinking water abstraction points; and efficacy of current drinking water purification techniques to remove the important cytotoxic drugs from river water.