Endotoxin health risk associated with high pressure cleaning using reclaimed water

- A partition model was developed to estimate inhalation and ingestion exposure from sprays.
- We modelled inhalation exposure risks from endotoxin in reclaimed water.
- Exposure from both domestic and occupational car washing was considered.
- Reclaimed water without filtration may pose a health risk for occupational spray use.

As water scarcity increases globally, reclaimed water is becoming an increasingly valuable and environmentally sustainable water source. In particular, use of reclaimed water in occupational settings involving high volume water use can potentially confer significant benefits. Prior to expansion of the use of reclaimed water, it is important that potential health risks associated with different modes of exposure are thoroughly investigated. Reclaimed water regulation has predominantly focused on health risks presented by enteric pathogens via ingestion of contaminated water; however, less is known about the risk of infection and inflammatory responses associated with inhalation exposures. High pressure cleaning has been identified as causing increased exposure to aerosol components and is an activity performed in both domestic and occupational settings. We developed a method to estimate water exposure volumes deposited into the lungs during high pressure cleaning. This was achieved by using data from two earlier experimental studies: one which quantified the size distribution of aerosols generated by a high pressure spray device and another which measured the total volume of water ingested and/or inhaled by subjects undertaking a 10 min car washing activity. Using available information about endotoxin levels in reclaimed water and the deposition profile of aerosol particles in the lungs, we used Quantitative Risk Assessment to model the health risks of exposure to high pressure cleaning sprays. The model results suggest that using reclaimed water treated without membrane filtration may pose a health risk to workers spending 6 h per working day using high pressure sprays. In contrast, use of reclaimed water in domestic settings is likely to result in inhaled endotoxin exposures below the No Observed Effects Level (NOEL) even for reclaimed water without membrane filtration treatment. While this case study pertains to the cleaning of vehicles, it is relevant to the broader use of high pressure cleaning devices, illustrating how health risks associated with inhalation exposure may be determined for a range of water types and contaminants to inform the design of appropriate water treatment and other intervention measures. It is also the first time that experimental water exposure data have been combined with aerosol generation and deposition data to partition ingestion and inhalation exposure volumes. This method restricts upper estimates of exposure volumes that might otherwise be overestimated if it was assumed that all aerosols generated from the high pressure device were inhaled.