World Environmental Health Day 2025 - The Hidden Power of Bad Odours: How smell shapes our health

What’s the worst smell you can remember? A bin left out in the heat? Damp creeping through an old flat? That acrid note of traffic on a humid evening. These things stick. They colour how we feel about a street, a building, a whole day.

This year’s theme for World Environmental Health Day, is Clean Air, Healthy people. We often think of clean air in relation to pollutants, but odour is also a big part of clean air. How a place smells can affect sleep, stress and mood more than we think.

The science bit

Smell is wired straight into our brain’s emotion and memory centres - the limbic system - which is why a whiff can calm us or set our nerves on edge in a heartbeat.

Bad odours can have a surprisingly large impact on us - we can react to certain odours before concentrations reach toxic levels. Nausea, headache and irritability are well-documented acute responses, and persistent annoyance can push up our stress hormones, disrupt sleep and chip away at our quality of life.

A systematic review of industrial odour exposure linked sustained odour annoyance to poorer self-reported health and wellbeing, and studies from both agricultural and urban settings find higher psychological distress among the most annoyed groups.

None of this proves that an odour is “toxic” on its own. It says something rational, backed by evidence: unpleasant smells change how we feel and function, and they’re often early flags that conditions need a closer look.

A day in smells (and what it tells you)

Think of the day by scent:

Morning coffee: comfort
School-run exhaust fumes: irritation
Office air: staleness
Gym sweat and disinfectant: tolerated
Dinner on the way home: anticipation

These small signals add up to how we judge spaces. Some areas might carry crisp, clean air whilst others live with background notes from waste handling, traffic, wastewater or food businesses. In England, the waste sector accounts for a large share of serious incidents at permitted sites, with odour repeatedly cited by the Environment Agency as a community concern.

Stories about the ‘smelliest’ towns may grab headlines but the reality is more serious. Local teams aren’t just there to enforce the law, they are protecting the public from the very real impacts that nuisance odours can have on wellbeing. Councils often have a duty to investigate complaints, whether it’s from waste sites, restaurants or farms, because bad odours will erode sleep, increase stress, and diminish our living standards even when pollutant levels are technically safe.

Investigating odours, gathering evidence, and engaging with businesses all take time and expertise. While enforcement is the legal tool, the true value of environmental health is in prevention and in safeguarding communities before problems escalate. It is about giving people the confidence that their environment is safe and liveable.

A simple invitation

Before you scroll on, take 10 seconds. What does your day smell like right now? Fresh, musty, sharp, or sweet? If something feels “off,” your nose might be ahead of the data. That doesn’t mean panic. It means the environment is tapping you on the shoulder. A sulphurous smell may signal hydrogen sulphide issues from a waste site. A musty note often points to damp or mould and a ventilation problem.

Odours won’t replace measurements. But they’re part of the evidence of lived experience - a fast, human signal that helps us notice problems early and, ultimately, live more comfortably wherever we are.