The THP hazard rating approach was developed by the Organization for Economic Co-operation and Development (OECD, Paris, France) in 1982. Individual relative risk levels and the overall THP value constitute the two components of this approach .(OECD, 1982) The THP rating approach consists of three variables: Toxicity to the aquatic environment (T), hazard to human health by oral intake (H) and the persistence rating value (P), which is related to the probable half-life expressed in days.
The THP rating approach can be used to compare and rate the hazards that pesticides pose to humans, wildlife, and the overall ecosystems through exposure to water and land. To better understand and refine contaminant fate and transport, risk indicators could be integrated with forensic methods (e. g., chemical and/or isotopic fingerprinting, contaminant transport models, geographic information system (GIS) representation and statistical methods) to reduce limitations of risk indicators and improve the risk assessment evaluation (Muhammetoglu et al., 2010).