For Elaine Corner, stepping into the garden on a summer’s day feels as intolerable as “walking behind an open bin lorry”. Even with every window tightly shut in Elaine Corner’s home in the English market town of Westbury, the retired teacher frequently cannot escape the nausea‑inducing stench that drifts from a nearby waste treatment plant. Elaine Corner remarks, “We can’t use our garden or go for a walk, you feel as though you’re going to vomit.”

Most of us have, at one time or another, caught the rank whiff of decomposing waste while emptying a rubbish bin, driving past a landfill, or passing a factory that emits a sickly pong. Now, imagine that fleeting encounter turned into a permanent, daily reality.

Society often treats odour pollution as a trivial nuisance, relegating it to the realm of personal preference. Research consistently shows that people rank their sense of smell lower than vision, hearing, touch, and taste. In fact, a survey of United States college students revealed that a significant number would rather part with their sense of smell than lose their smartphone.

Beyond the immediate discomfort, a growing body of scientific evidence links unpleasant urban odours to a spectrum of health complaints, ranging from headaches and nausea to breathing difficulties and disturbed sleep. These odours can also trigger longer‑term mental and physiological responses. The expanding research landscape is gradually uncovering just how influential scent can be for overall wellbeing.

The scent of danger

Smell has evolved, in part, as an early‑warning system that prompts avoidance of potentially harmful agents. A rancid, putrid smell often signals the presence of bacteria that could cause illness. According to Johan Lundström, a professor in the science of smell at the Karolinska Institute in Stockholm, Sweden, this evolutionary mechanism forms a key component of the human “behavioural immune system.” Johan Lundström explains, “The olfactory system primarily functions as an avoiding system to learn to warn us about danger in the environment.”

Neuroscientific studies have demonstrated that odour signals are processed in the brain within roughly 300 milliseconds after inhalation. Participants exposed to disagreeable smells exhibited rapid, instinctive physical reactions, such as immediately withdrawing from the source.

Because the default function of smell is defensive, it is relatively easy for the brain to label an unfamiliar odour as negative. Johan Lundström notes, “If we detect an odour and we don’t know what it is, it is almost always a negative experience.”

When a particular scent becomes associated with a threat, human sensitivity to that scent can increase dramatically. In an experiment led by Johan Lundström, participants who learned to pair a specific odour with a mild electric shock were later able to detect the same odour at concentrations far below the usual detection threshold. This heightened sensitivity likely served an evolutionary purpose: it enables swift reactions to faint but potentially dangerous cues. The characteristic rotten‑egg smell of hydrogen sulfide – a gas emitted by sewage treatment processes – can be perceived at concentrations as low as 0.5 parts per billion, acting as an early alarm for a substance that becomes lethal at higher levels.

Real health impacts

Odour does not merely function as a danger detector; it also exerts tangible effects on wellbeing. Pleasant aromas, such as the fragrance of a temperate woodland, have been shown to boost mental health by activating brain regions involved in emotion and memory.

Conversely, exposure to foul odours can be detrimental. A 2021 systematic review of multiple investigations identified a “biological plausibility” linking headaches, vomiting, and other symptoms to unpleasant scents. One proposed mechanism is the activation of the vagus nerve—a major conduit between the brain and gastrointestinal tract—by noxious odours, which can provoke nausea and vomiting. Nevertheless, the authors of that review emphasized the need for further research to definitively establish physiological pathways.

The magnitude of health effects also hinges on the psychological response to the odour. Pamela Dalton, a cognitive psychologist at the Monell Chemical Senses Center in Philadelphia, United States, who has spent more than three decades examining odour‑related health outcomes, observes, “The health impact is mediated through an individual dislike or fear of an odour.” In other words, the more anxiety Elaine Corner or any other individual feels about a smell, the stronger the potential impact on physical and mental health.

Lifestyle changes

A persistent foul smell can infiltrate many aspects of daily life, prompting what researchers label “maladaptive actions.” Those actions may include keeping windows closed on sweltering days, foregoing outdoor exercise, or canceling social gatherings. Elaine Corner notes that the constant stink in Westbury “affects your social life. If you’re planning a barbecue in the summer, you’re hoping it’s not going to stink you out.”

Responses to odour vary widely across the population. Some individuals report only occasional awareness of a smell or claim that it does not bother them at all. Pamela Dalton explains that factors such as age, gender, existing allergies, and lifestyle choices—including smoking—shape how a person perceives odours.

It is a common misconception that repeated exposure leads to habituation. In the case of noxious odors emanating from landfills, studies suggest that tolerance does not necessarily increase over time. By contrast, neutral or pleasant aromas are readily habituated to. Johan Lundström remarks, “Once you have smelt an odour, and identified that it’s not going to kill you, then you stop being able to smell it.” This explains why, despite the human nose’s ability to differentiate roughly one trillion distinct scents, many people struggle to name everyday smells such as coffee or vanilla.

Fighting a stink

Odour plumes are often fickle, shifting with wind direction or varying from one street to the next. Amanda Giang, associate professor of environmental modelling and policy at the University of British Columbia in Canada, describes this phenomenon as “hyper‑local.” Amanda Giang explains, “I could live a block away and never know that the block over it smells like rotting fish.”

Nevertheless, the burden of foul odours is not shared equally. Lower‑income neighbourhoods, which frequently feature cheaper housing, tend to be situated nearer to landfills, incinerators, and heavy‑industry facilities. European and United Kingdom studies have found that residents of low‑income communities are statistically more likely to live within a two‑kilometre radius of waste‑related sites than wealthier counterparts.

Public complaints about offensive smells can catalyze change. Community‑led campaigns have compelled sewage plants, fish‑processing factories, and similar operations to curtail or relocate their activities. In recent years, several governments have introduced stricter odour‑control regulations—for example, new limits on emissions from fish‑feed plants in Chile and tighter permissible stink thresholds for industrial sites in residential zones in Lithuania.

Odorous benefits

Even for residents of neighbourhoods plagued by persistent foul scents, there is a modest silver lining: a well‑functioning sense of smell is itself an indicator of good health.

Research published in 2018 involving 70 adult participants demonstrated that individuals with heightened olfactory sensitivity reported greater enjoyment of food and a higher degree of pleasure during sexual activity. Among women with superior smell acuity, the frequency of orgasm during intercourse was also higher.

Conversely, the estimated five percent of the population who experience anosmia—complete loss of the sense of smell—often confront numerous health challenges. Interviews with people living with anosmia reveal reduced appetite and poorer dietary quality because meals become less enjoyable. Johan Lundström observes, “If you lose your sense of smell, you will notice that your appetite goes away.”

More strikingly, longitudinal studies have linked diminished olfactory function with a 46 % higher risk of mortality within a ten‑year span among older adults. While the exact mechanisms remain under investigation, correlations have emerged between reduced smell and deaths from cardiovascular disease as well as neurodegenerative disorders such as Alzheimer’s disease and Parkinson’s disease.

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“As someone who’s researched odours for decades,” says Pamela Dalton, “I don’t mind smelling bad odours because it means my sense of smell is really working!”

For Elaine Corner and other Westbury residents, the reality is far less pleasant. Hills Waste Solutions, the operator of the nearby waste treatment plant, has indicated that it is collaborating with the Environment Agency to address the community’s odour concerns.

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