From Environmental Hazard to Human Dose

Health effects occur in people.

Environmental contamination occurs in environmental media.

Between them lies an exposure pathway.

Hazard

The substance must first possess properties capable of causing harm.

This is the hazard.

Hazard alone does not identify how much reaches a person.

Release

A release transfers material across the boundary being assessed; direct contact can also occur within a workplace or contained system.[R01]

Release may occur into air, water, soil, food or indoor environments.

Containment therefore needs to be assessed together with possible routes of contact.[R01]

Transport

Environmental processes determine where the substance goes.

These may include dispersion, runoff, groundwater movement, deposition and biological transfer.

Exposure

Exposure occurs when a person contacts the contaminant.

Important routes include inhalation, ingestion and dermal exposure.

Dose

Dose concerns how much enters or reaches the body over time.

Dose depends on environmental concentration, exposure frequency, duration, route, behaviour and physiology.

Internal dose

For some substances, further analysis may consider how much is absorbed and distributed within the body.

This is different from simply measuring environmental concentration.

Duration

Acute and chronic exposures present different questions.

Acute

Short-duration exposure, potentially at elevated concentration.

Chronic

Repeated or sustained exposure over long periods.

Toxicological consequences can differ.

Evidence

Moving from environmental measurement to demonstrated health consequence may involve toxicology, epidemiology, biomonitoring, exposure modelling and clinical evidence.

Different methods provide different parts of the causal picture.

Governing sequence

Hazard → Release → Environmental Transport → Exposure → Dose → Potential Health Effect.

Skipping stages may overstate certainty.

Understanding them enables more precise prevention.