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Study points out that air pollution can silently and progressively reduce the sense of smell, affecting millions without clear symptoms.
In 2024, a study published in Scientific Reports on December 16, 2024, from the Nature group, brought an alert little explored outside the academic community: continuous exposure to air pollution may be associated with the progressive reduction of olfactory capacity, in a silent and cumulative process over the years. In the work, researchers cross-referenced data from 711 urban participants from 10 regions of the world with atmospheric pollutant levels measured on the dates and at the locations of the tests and concluded that pollution negatively affects olfactory function, with an impact that tends to accumulate with aging.
The most relevant point is that this loss does not necessarily appear abruptly, which helps explain why many people may not notice the problem as it progresses. The study itself states that the effects of pollution on the sense of smell are cumulative and cites previous evidence of progressive worsening even in contexts where pollution levels only slightly exceeded WHO standards.
At the same time, the World Health Organization, in a fact sheet published on October 24, 2024, classifies air pollution as one of the main environmental risks to human health. According to the entity, outdoor air pollution was associated with approximately 4.2 million premature deaths per year in 2019, while the sum of the effects of outdoor and household pollution is linked to 6.7 million premature deaths annually, with an impact on the cardiovascular, respiratory, and other central mechanisms of the body.
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How pollution directly interferes with the olfactory system
The sense of smell depends on a highly sensitive system located in the upper part of the nasal cavity, where receptor cells capture odor molecules and send signals directly to the brain.
When a person is continuously exposed to pollutants, such as fine particulate matter (PM2.5), nitrogen dioxide (NO₂), and ozone (O₃), these substances can cause chronic inflammation of the nasal mucosa, in addition to directly damaging the cells responsible for odor detection.
Studies suggest that ultrafine particles may not only reach these structures but also penetrate deeper, affecting neural pathways associated with olfaction. This creates a scenario where the damage is not just local but can involve broader neurological connections.
The result is a progressive reduction in sensitivity, making it more difficult to identify common everyday smells, such as food, smoke, or even hazardous substances.
A cumulative effect that can go unnoticed for years
Unlike other sensory changes, such as sudden hearing loss or vision problems, olfactory loss associated with pollution tends to occur slowly.
This means that the brain gradually adapts to the reduction in sensory capacity, creating a false sense of normalcy. The person continues to live normally, unaware that their perception of odors is being diminished.
This phenomenon is known as sensory adaptation, and it is one of the main reasons why the problem remains invisible. When the individual finally notices some change, the impairment may already be advanced.
Impacts that go beyond smell and affect overall health
Loss of smell is not just a sensory issue. It is directly linked to several important functions of the body.
Smell plays a fundamental role in risk detection, such as gas leaks, spoiled food, or the presence of smoke. Its reduction can increase exposure to dangerous situations without the person realizing it.
Furthermore, smell is closely connected to taste. The decrease in the ability to sense odors can affect the perception of food flavors, leading to changes in eating habits and even nutritional deficits.
Research also indicates an association between olfactory loss and cognitive decline, as well as possible links to neurodegenerative diseases, although this area is still under investigation.
Who is more exposed to risk
Although the entire urban population is potentially exposed, some groups are more vulnerable.
Residents of large urban centers, especially in areas with heavy traffic, tend to have greater contact with pollutants. Workers exposed to outdoor air for long periods, such as drivers, delivery personnel, and construction professionals, may also experience more significant impacts.
Children and the elderly represent particularly sensitive groups. In the case of children, the respiratory and neurological systems are still developing. In the elderly, exposure may accelerate natural processes of sensory loss.
The role of cities in amplifying the problem
Intensive urbanization and the increase in vehicle fleets have contributed to rising air pollution levels in various regions of the world.
According to the WHO, more than 90% of the global population breathes air that exceeds recommended quality limits. This means that billions of people are exposed daily to potentially harmful levels of pollutants.
Moreover, factors such as population density, lack of green spaces, and climatic conditions can exacerbate the concentration of pollutants in certain cities, further increasing the risk of prolonged exposure.
Why this issue is still little discussed
Despite scientific advances, the relationship between air pollution and olfactory loss is still not widely known by the public.
This happens because the topic is often overshadowed by more immediate and visible effects, such as respiratory or cardiovascular diseases. However, the impact on smell represents an additional dimension of the problem, which can significantly affect quality of life.
Another factor is the difficulty of measuring olfactory loss in daily life. Unlike blood tests or blood pressure checks, olfactory assessment is not part of routine check-ups, which contributes to the underreporting of the problem.
What science has proven and what is still under study
The association between air pollution and reduced olfactory function already has a consistent scientific basis, with observational studies and population analyses pointing to this relationship.
However, there are still ongoing investigations to better understand the exact mechanisms involved, the degree of reversibility of the damage, and which pollutants have the greatest specific impact on the olfactory system.
Researchers are also seeking to identify ways to mitigate these effects, whether through public policies for pollution reduction or individual interventions.
An invisible effect that can affect millions without them noticing
The main characteristic of this phenomenon is precisely its invisibility. There is no immediate alert, no intense pain, and in most cases, no early diagnosis.
The sense of smell may be silently diminishing while the person continues to be exposed to the same levels of pollution in daily life. This type of impact reinforces the need to broaden the debate on air quality, not only as an environmental issue but as a direct factor of sensory and neurological health.
And you, have you noticed changes in your sense of smell over the years?
Science is beginning to reveal that the air we breathe can influence senses that we rarely associate with pollution. Have you noticed greater difficulty in smelling or do you think this might be happening without you realizing it?
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