Chemical risk & exposure
Exposure pathways explained: how a chemical gets from the drum to a person
A chemical can only harm someone if there is a complete pathway from the source to them. Break any link in the chain and the exposure stops.
An exposure pathway is the route a chemical takes from where it starts to the person or ecosystem it affects. Every complete pathway has the same links:
- Source: where the chemical comes from, such as a tank, a spray rig, a waste pit or a burning heap.
- Release mechanism: how it escapes, through a leak, spill, evaporation, dust or smoke.
- Transport medium: what carries it, which can be air, water, soil or food.
- Point of contact: where people or animals meet it, such as a borehole, a field, a workshop or a playground.
- Exposure route: how it enters the body, by inhalation, skin contact, ingestion or injection.
- Receptor: who or what is exposed, such as workers, residents, children, livestock or fish.
Four common pathways
| Source | Pathway | Receptor and route |
|---|---|---|
| Pesticide sprayed on crops | Spray drifts on the wind to nearby homes | Residents breathe it in |
| Fuel leak from a generator | Seeps into soil, then groundwater, then a borehole | Families drink the water |
| Burning plastic waste near a school | Smoke carries particles and toxic gases | Children breathe it in |
| Chemicals dumped on farmland | Taken up from soil by crops | People eat the vegetables |
The four routes of entry
- Inhalation of gases, vapours, mists, dust and fumes. This is the most common route at work.
- Skin and eye contact, through splashes and contaminated surfaces and clothing. Some solvents and pesticides pass straight through the skin.
- Ingestion, usually accidental: eating, drinking or smoking with contaminated hands, or using mislabelled containers.
- Injection, through cuts from contaminated sharps or broken glass, or high-pressure equipment.
Why the pathway approach helps. It turns a general worry ("this chemical is toxic") into specific places to act. If there is no pathway, there is no exposure. If there is one, you can choose the cheapest link to break: contain the source, block the release, protect the water supply or change the task.
What to do
- In ESIAs and site risk assessments, map at least one complete pathway for each significant chemical.
- Remember receptors outside the fence: neighbours, wells, gardens and schools.
- Check that controls break the pathway early, at the source or release, rather than relying only on PPE at the receptor.
How INRC can help
We map exposure pathways for workers and neighbouring communities in our ESIAs, and use our environmental monitoring service to check air, water and soil at the points where people could be exposed. Contact us to discuss your site.
This article is general guidance, not legal advice. Check current legislation and regulations for your specific project.