API PUBL 4733 pdf download.Risk-Based Screening Levels for the Protection of Livestock Exposed to Petroleum Hydrocarbons 3. Conceptual Site Model A conceptual site model (CSM) identifies complete and potentially complete exposure pathways and receptors to be considered in a risk assessment. If no complete significant pathway(s) exist for exposure of livestock to petroleum hydrocarbons, a screening-level risk evaluation for livestock...