Environmental and occupational toxicology
How air pollution, solvents, pesticides and other chemicals at home and at work harm health, and how exposure is controlled.
Most people never overdose on a drug, but everyone breathes polluted air or meets chemicals at work. This field studies long, low-level exposures as well as accidents: the pollutants, the organs they damage, the limits set by regulators and the controls that protect workers.
Air pollutants
Fine particles penetrate deep into the lungs and are the main health concern; ozone forms in sunlight from traffic emissions; nitrogen and sulfur oxides come from burning fuel. WHO attributes millions of premature deaths each year to outdoor air pollution, most of them in low- and middle-income countries, mainly from heart disease and stroke. Indoor smoke from cooking fuels adds to the burden.
Carbon monoxide
Carbon monoxide comes from incomplete burning in faulty heaters, stoves and engines. It binds haemoglobin in place of oxygen. Early symptoms (headache, dizziness, nausea) are easily mistaken for flu; severe exposure brings confusion, unconsciousness and lasting brain damage. Treatment is fresh air and oxygen, sometimes hyperbaric oxygen. Detectors near gas appliances prevent it.
Solvents and industrial chemicals
Aromatic hydrocarbons such as benzene, toluene and xylene are common solvents. Short exposures depress the nervous system; long exposure to benzene injures the bone marrow and increases the risk of leukaemia. Workplace limits for such chemicals are set from dose–response data and reviewed over time.
Pesticides
Insecticides are generally more toxic to people than herbicides. Organophosphates and carbamates cause the cholinergic toxidrome; some herbicides, such as paraquat, cause delayed lung injury. Those spraying need protection and bystanders should stay away during and after spraying. International bodies set residue limits for food, and WHO seeks bans on the most toxic and persistent products.
Protecting workers
- Elimination: remove the hazard.
- Substitution: use a safer chemical.
- Engineering controls: ventilation, enclosure, barriers.
- Administrative controls: shorter or less frequent exposure, training.
- Personal protective equipment: gloves, masks, suits; the last line, not the first.
Test yourself
Think of the answer, then tap the question to see it.
Why is carbon monoxide poisoning often missed?
The gas cannot be seen or smelled and early symptoms (headache, dizziness, nausea) resemble a viral illness.
Which workers face the greatest risk from pesticides?
Farm workers who apply them, and people nearby during and shortly after spraying.
Which organ does long-term benzene exposure damage, and with what consequence?
The bone marrow; it raises the risk of leukaemia and other blood disorders.
Why is personal protective equipment the last step in the hierarchy of controls?
It depends on each worker using it correctly; the higher steps remove or contain the hazard without relying on behaviour.
Example drugs
Connections
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Ambient (outdoor) air pollution (World Health Organization, 2026); Pesticide residues in food (World Health Organization, 2026); Hierarchy of Controls (National Institute for Occupational Safety and Health (NIOSH), CDC, 2026); Carbon monoxide poisoning: MedlinePlus Medical Encyclopedia (MedlinePlus (U.S. National Library of Medicine), 2026).
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Representative model, for educational purposes only.