Exposure assessment using tracer chemicals – Stage 1

There are concerns that recycled wastewater used for watering gardens or washing cars might be accidently ingested. The problem with this is that water for irrigation is not recycled to the same high (and expensive) standard as potable drinking water and might contain pathogens that cause diarrhoea and illness. Recycled water providers must quantify the risk that irrigation water might pose to public health, even though it is not supposed to be drunk. This research worked on the first part of this health risk quantification problem by developing a method to measure the amount of water a person might ingest while, for example, washing a car. Harmless cyanuric acid is commonly added to swimming pools and swimmers often ingest pool water. The amount of cyanuric acid measured in their urine is related to the volume of pool water they ‘drank’. Domestic users of recycled water are more likely to ingest less recycled water than swimmers, so a more sensitive ‘GCMS’ method for measuring very low levels of cyanuric acid was developed. It was shown to work after cyanuric acid was added to water, drunk by three adult volunteers, and then measured in their urine.