Odour pollution: what it is, causes, effects and solutions

Odour pollution is an increasingly relevant environmental issue due to its negative impact on public health and quality of life. Although often seen as a minor nuisance, its consequences can be significant for both human health and the environment. In this article, we will explore what the problem of odour pollution is, its most common causes, and how it can be effectively addressed to improve the air we breathe.

What is odour pollution?

Odour pollution, also referred to as environmental odour nuisance, is defined as the presence of unpleasant-smelling substances in the air that cause discomfort or distress to people. These odours typically originate from industrial, agricultural, domestic or urban sources, negatively impacting the perceived environmental quality.

This type of pollution is more than a nuisance; it can seriously degrade air qualityAir quality refers to the state of the air we breathe and its composition in terms of pollutants present in the atmosphere. It is considered good when poll...
Read more, affecting people’s physical and emotional wellbeing. Scientific studies have shown that long-term exposure to offensive odours can increase stress, anxiety and even trigger respiratory problems, especially in vulnerable groups such as children or the elderly.

There is also a notable link with noiseImagine waking up every morning at 5:00 a.m. to the relentless roar of a motorway just metres from your window. Experiencing such high-intensity noise is n...
Read more pollution, as both often coexist in densely populated urban and industrial areas, exacerbating the perceived environmental stress of residents.

Main causes of odour pollution

Industrial and agricultural sources

Industrial and agricultural activities are major sources of odour emissions due to the chemical and biological processes they involve. Key contributors include:

• Waste treatment: Urban solid waste management facilities and wastewater treatment plants (WWTPs) generate strong odours due to organic decomposition.
• Intensive livestock farming: Pig farms, poultry facilities and cattle stables emit gases such as ammonia and hydrogen sulphide, which are responsible for strong odours.
• Chemical and petrochemical plants: These sites release volatile compounds with characteristic, penetrating smells, derived from specific chemical processes.

These sources require specific measures for odour control, such as advanced technologies like smart sensors for real-time odour monitoring. Specialised companies provide advanced solutions to support effective environmental management in industrial settings.

Urban and domestic pollution

Everyday urban and household activities also contribute significantly to odour nuisance. Common causes include:

• Poor household waste management: Improper disposal or accumulation of domestic waste leads to odours from organic decomposition.
• Inadequate sewage systems: Poorly managed wastewater emits foul smells that directly affect urban life quality.
• Volatile organic compounds (VOCs): These chemicals evaporate easily at room temperature and are found in everyday products like paints, solvents and cleaners, generating intense and unpleasant odours.

VOCs are not only unpleasant—they can be hazardous to health when found in high concentrations indoors, making proper air quality monitoringControlling air quality is an essential task in order to enjoy optimal environmental conditions for healthy human development and to keep the environment i...
Read more essential.

To tackle these challenges, cities are turning to continuous air monitoring technologies using sensors that can accurately identify the source of odours, enabling the implementation of effective mitigation strategies. Kunak Technologies, for instance, offers dedicated sensors to monitor odour pollution, helping cities and companies manage this environmental challenge smartly and efficiently.

Effects of odour nuisance on health and the environment

Health consequences

Odour pollution is more than a sensory inconvenience—it can have severe implications for human health. Recent scientific studies reveal that long-term exposure to unpleasant odours may cause:

• Respiratory issues: Continuous exposure to irritant gases like ammonia or hydrogen sulphide—common in odour emissions—can trigger airway irritation, coughing, bronchitis, and worsen asthma or COPD (chronic obstructive pulmonary disease).
• Stress and psychological distress: According to a 2022 study published in Environmental Health Perspectives, persistent exposure to offensive odours is linked to higher levels of stress, anxiety and sleep disturbances, all of which affect emotional wellbeing and quality of life.
• Reduced quality of life: The discomfort caused by odour nuisance affects concentration, productivity and mood, particularly in communities close to major odour sources.

These cumulative effects underscore the need for proper and preventive environmental odour assessment to safeguard public health.

Environmental impact

Beyond human health, odour pollution also disrupts the local ecosystem in several ways:

• Impact on wildlife: Many animals rely on scent cues for survival and behaviour. Exposure to abnormal or contaminating odours can disrupt feeding, reproduction and migration patterns.
• Damage to vegetation: Emissions of odorous gases like ammonia can acidify soils and alter their chemical composition, negatively affecting plant growth and biodiversity.
• Degraded surroundings: Communities near odour-emitting sources often experience a general decline in environmental quality, with impacts including reduced property value and social resistance to certain industrial activities.

These effects highlight the importance of treating odour pollution as a comprehensive environmental issue requiring both technical intervention and effective regulation.

Techniques for measuring and assessing odours

Olfactometry: what it is and how it works

Olfactometry is the internationally recognised standard technique for objectively measuring odours in the air. Its purpose is to quantify odour intensity, concentration, and quality using trained human assessors capable of identifying specific odours.

• Odour concentration is measured in units known as ouE/m³ (European odour units per cubic metre).
• The most widely used method is dynamic olfactometry, which involves progressively diluting a contaminated air sample until the odour is no longer detectable by the sensory panel.
• This technique, while precise, requires specialised laboratories and is costly for continuous monitoring.

Olfactometry remains the reference method for scientific studies and environmental odour assessments, playing a vital role in validating the effectiveness of odour control strategies.

Smart sensors and environmental monitoring

Recent technological advances have led to the development of intelligent electronic sensors capable of detecting and measuring odours in real time, enabling automated, continuous air quality monitoring.

• These sensors use technologies such as chemical and optical sensors, combined with artificial intelligence, to analyse air composition and detect odorous compounds.
• They allow for immediate identification of pollution sources and continuous tracking, enhancing responsiveness and environmental management.
• Leading companies now offer technological solutions that integrate high-precision sensors with digital platforms for real-time data visualisation and smarter decision-making.

This technological evolution marks a key breakthrough in odour control, enabling both authorities and industries to ensure more efficient and transparent environmental management.

Solutions and control measures to reduce odour pollution

Industrial strategies

Effectively mitigating unpleasant odours in industrial environments requires a combination of techniques and best practices, including:

• Air treatment and filtration: Systems such as biofilters, activated carbon filters, and advanced oxidation units help eliminate or significantly reduce odorous compounds before they are released into the atmosphere.
• Efficient waste management: Improving the handling of organic waste, controlling fermentation and decomposition, and applying controlled composting techniques help minimise odour generation.
• Process maintenance and control: Regular inspection of equipment and processes is essential to avoid leaks or accidental emissions that contribute to odour emissions.
• Gas monitoring: Installing perimeter sensor networks that detect odorous gases in real time allows for the rapid identification of emissions and immediate action to reduce odours. Continuous monitoring helps ensure regulatory compliance, improves processes, and enhances communication with communities and authorities. Advanced technologies, such as those offered by Kunak, integrate smart sensors with digital platforms to deliver efficient and transparent odour pollution control.

Ideally applied in combination, these measures form the foundation of comprehensive and effective odour management strategies in industry.

Environmental regulations and standards

Controlling odour pollution is grounded in regulatory frameworks that set limits, procedures and responsibilities for emitters and authorities alike. Below are key regulations from Europe, Latin America and the United States, including specific data and official links.

Spain: Order ARM/1783/2013

In Spain, odour regulation is covered under Order ARM/1783/2013, which sets out criteria for evaluating and controlling emissions in industrial and urban facilities. The regulation imposes maximum continuous emission limits of 1 ouE/m³ in sensitive areas and allows peaks of up to 5 ouE/m³ in industrial zones. It also requires the use of dynamic olfactometry for measurement and mandates that facilities include odour reduction plans in their environmental licences. Further information is available on Spain’s official BOE website.

Germany: TA Luft (2021)

Germany has one of the strictest regulatory frameworks for atmospheric emissionsAtmospheric emissions are pollutants emitted into the air, mainly as a result of human activities such as industry, transport by combustion vehicles and en...
Read more, including odours, primarily governed by the Umweltbundesamt TA Luft. While it does not specify limits in odour units, it sets tight controls on odour-related gases such as ammonia, with a limit of 5 mg/m³. TA Luft also requires continuous monitoring systems and periodic reports to environmental authorities, with penalties including fines or operational suspensions for non-compliance.

France: National Odour Prevention Plan (PNPO)

France takes a comprehensive and pioneering approach in Europe with its National Odour Prevention Plan (PNPO), which sets a maximum odour concentration limit of 3 ouE/m³ in sensitive urban areas. The regulation obliges industries to implement control measures, conduct regular assessments, and maintain open communication with affected communities. It also mandates that odour emissions be included in environmental permits with corresponding mitigation and monitoring plans. Official information can be found on the Ministère de la Transition Écologique website.

Mexico: Official Mexican Standards (NOM)

Mexico regulates pollutant emissions, including odorous compounds, through the NOM-085-SEMARNAT-2011 standard. This limits total VOCs to 200 mg/m³ in certain industries, aiming to minimise nuisance odours. It also mandates emission reports and mitigation plans for industrial establishments.

Brazil: CONAMA Resolution 382/2006

Brazil’s CONAMA Resolution 382/2006 broadly governs environmental management and includes odour emissions from industrial and agricultural activities. It promotes the use of olfactometry and continuous monitoring in critical areas, requiring industries to implement environmental management plans to reduce odours.

Argentina: National Environmental Management Law and Resolution 177/2020

Argentina’s National Environmental Management Law (Law 25.675) and Resolution 177/2020 establish the framework for environmental protection, including regulation of odorous emissions. The latest resolution outlines procedures for environmental impact assessments that consider odours and require specific studies and mitigation plans. More information is available on InfoLeg.

United States: State-level regulations

In the US, there is no unified federal regulation specifically for odours, but several states have their own rules. California, through Title 17, Section 93110 of the California Code of Regulations, regulates fugitive emissions from sectors like wastewater treatment, setting specific limits for gases such as hydrogen sulphide at typical levels of 10 ppb. Other states, including Texas and Florida, also have regulations requiring odour control and reporting in industrial and agricultural facilities.

The importance of regulatory compliance

Strict compliance with these regulations helps to:

• Protect public health and improve quality of life.
• Reduce social conflict and improve acceptance of industrial and agricultural projects.
• Avoid economic penalties and activity suspensions.
• Promote technological innovation, such as real-time monitoring solutions from Kunak.

This global framework highlights the growing importance of addressing odour pollution with solid technical and regulatory approaches tailored to different geographical and economic contexts.

Summary of international regulations

Country / State	Regulation	Key limits	Core procedures	Official link
Spain	Order ARM/1783/2013	1 ouE/m³ (sensitive areas), 5 ouE/m³ (industrial peaks)	Dynamic olfactometry, environmental permits	BOE
Germany	TA Luft (2021)	No ouE/m³ limit; ammonia ≤ 5 mg/m³	Continuous monitoring, regular reporting	Umweltbundesamt
France	National Odour Prevention Plan (PNPO)	3 ouE/m³ in sensitive urban areas	Regular assessment, community communication	Ministry of Ecology
Mexico	NOM-085-SEMARNAT-2011	Total VOCs ≤ 200 mg/m³	Emission reports, mitigation plans	DOF
Brazil	CONAMA Resolution 382/2006	No specific ouE/m³ limit	Olfactometry and continuous monitoring	CONAMA
Argentina	Law 25.675 and Resolution 177/2020	Impact study includes odours	Odour studies, mitigation planning	InfoLeg
California, USA	CCR Title 17, Section 93110	H2S typical limit: 10 ppb	Fugitive emission control and monitoring	CalEPA
Texas and Florida, USA	State-level regulations	Variable limits by compound	Industrial odour control and reporting	Various state portals

FAQs about odour pollution

What can I do if I live near a source of unpleasant odours?

If you live close to an odour-emitting source, it’s recommended to identify and document the nuisance and report it to the relevant environmental authorities. Participating in community meetings or forums can also help push for collective solutions. At home, using air purifiers can improve indoor air quality. There are also specialised technologies, such as those offered by Kunak, which support odour monitoring and community-level management.

Are unpleasant odours harmful to health?

While unpleasant smells don’t always indicate the presence of toxic substances, frequent exposure can cause eye, nose and respiratory irritation, as well as increase stress, anxiety, and affect mental health. Therefore, odour pollution should be treated as a serious issue that negatively impacts quality of life.

Which institutions regulate odour pollution?

Regulatory bodies vary by country, but typically include national and regional environmental agencies, local control authorities, and, in some cases, international organisations such as the World Health Organization (WHO). These institutions establish limits, regulations, and methods to measure and control odour emissions, ensuring environmental and public health protection.

How is odour intensity measured?

Odour intensity is primarily measured using a technique called olfactometry, which evaluates the human perception of a contaminated air sample. This involves trained panel members who detect and rate odour presence at various dilution levels.

The results are expressed in European odour units (ouE/m³), a standardised measurement of odour concentration per cubic metre of air. One odour unit corresponds to the minimum concentration detectable by 50% of the evaluating population. In other words, if the air has a concentration of 1 ouE/m³, half of the people tested can detect the odour in that volume of air.

In addition to traditional olfactometry, electronic sensors are increasingly used to detect and quantify odorous compounds in real time. These sensors allow continuous monitoring and provide precise data that complement human assessment, supporting more efficient odour pollution management.

What technologies are currently available to reduce odours?

There are various technologies to reduce odours, including biofilters, activated carbon filters, and chemical or biological treatments that neutralise odorous compounds. Smart sensors are also used for continuous odour monitoring, enabling quick and effective response. Companies like Kunak Technologies lead the development of integrated solutions to manage odour pollution.

Conclusions and final recommendations

Odour pollution is a complex environmental problem affecting human health, psychological wellbeing, and ecological balance. Effective management requires a multidisciplinary approach that combines advanced technology, sound industrial practices, and strict regulation.

To move forward in reducing this issue, the following actions are recommended:

• Citizens: Stay informed and actively participate in monitoring and reporting pollution sources.
• Industries: Implement monitoring and treatment technologies, and maintain good practices in waste and emissions management.
• Governments: Strengthen regulations, conduct regular inspections, and promote the use of innovative technologies such as those offered by Kunak for effective and transparent control.

Only with joint commitment can we improve air quality and protect public health, ensuring healthier and more sustainable environments for future generations.

Sources consulted:

• (1) Sucker, K., Both, R., & Winneke, G. (2001). Adverse effects of environmental odours: reviewing studies on annoyance responses and symptom reporting. Water Science And Technology, 44(9), 43-51. https://doi.org/10.2166/wst.2001.0505
• (2) Conti, C., Guarino, M., & Bacenetti, J. (2020). Measurements techniques and models to assess odor annoyance: A review. Environment International, 134, 105261. https://doi.org/10.1016/j.envint.2019.105261
• (3) Suffet, I.; Braithwaite, S. (2019) Odor complaints, health impacts and monitoring methods (white paper). University of California, Los Angeles. Accessed on 15/05/2020 at https://ww2.arb.ca.gov/sites/default/files/classic//research/apr/past/18rd010.pdf
• (4) Eusebio, L., Capelli, L., & Sironi, S. (2016). Electronic Nose Testing Procedure for the Definition of Minimum Performance Requirements for Environmental Odor Monitoring. Sensors, 16(9), 1548. https://doi.org/10.3390/s16091548