Source-Pathway-Receptor

The Source-Pathway-Receptor model describes the strict causal chain through which environmental harm occurs. A source creates a hazard, including a heavy fuel tank. A pathway enables physical transfer, including groundwater flow.

A receptor experiences the adverse effect, including a drinking water aquifer. Harm only arises when all three components connect. The term exists to impose rigorous causal discipline on risk management.

Risk is reduced when engineering decisions break the chain, rather than waiting to react to catastrophic outcomes. Removing the source, blocking the pathway, or isolating the receptor drops the risk to absolute zero. Failure occurs when operational controls focus exclusively on the receptor, including monitoring water quality, while the sources and pathways remain fully active.

The approach shifts effort downstream, preserving the exposure and relying entirely on the last line of defence. A defensible decision identifies the source, maps the pathway, names the receptor, and demonstrates precisely where the causal chain is completely broken. Monitoring the receptor measures the failure rather than preventing the disaster.

The most robust solutions break the chain directly at the source.