Spray irrigation of landfill leachate: estimating potential exposures to workers and bystanders using a modified air box model and generalised source term

Generalised source term data from UK leachates and a probabilistic exposure model (BPRISC4) 12 were used to evaluate key routes of exposure from chemicals of concern during the spraying 13 irrigation of landfill leachate. Risk estimates secured using a modified air box model are reported 14 for a hypothetical worker exposed to selected chemicals within a generalised conceptual exposure 15 model of spray irrigation. Consistent with pesticide spray exposure studies, the key risk driver is 16 dermal exposure to the more toxic components of leachate. Changes in spray droplet diameter 17 (0.02-0.2 cm) and to spray flow rate (50-1000 l/min) have little influence on dermal exposure, 18 although the lesser routes of aerosol ingestion and inhalation are markedly affected. The risk 19 estimates modelled using this conservative worst case exposure scenario are not of sufficient 20 magnitude to warrant major concerns about chemical risks to workers or bystanders from this 21 practice in the general sense. However, the modelling made use of generic concentration data for 22 only a limited number of potential landfill leachate contaminants, such that individual practices 23 may require assessment on the basis of their own merits.