Project – Indoor Air Quality and Respiratory Symptoms among Commercial Food Vendors: A Study of Food Vendors in Ikeja, Lagos State

CHAPTER ONE

INTRODUCTION

1.1 Background to the Study

Indoor air quality is an important environmental and occupational health concern because people spend substantial periods of their daily lives within enclosed or semi-enclosed spaces where pollutants can accumulate. Indoor air quality refers broadly to the physical, chemical and biological characteristics of air within buildings and other enclosed working environments and is influenced by ventilation, fuel combustion, cooking activities, building characteristics and the presence of indoor pollutants. Poor indoor air quality can expose workers to particulate matter, carbon monoxide, volatile organic compounds and other contaminants capable of irritating or damaging the respiratory system. The World Health Organization (WHO, 2021) identifies air pollution as a major public health risk and provides health-based guideline levels for pollutants including fine particulate matter (PM₂.₅), PM₁₀, nitrogen dioxide, sulfur dioxide and carbon monoxide. The WHO recommends a 24-hour guideline level of 15 µg/m³ for PM₂.₅ because exposure to fine particulate matter is associated with respiratory and cardiovascular health effects. Therefore, maintaining acceptable indoor air quality is important for protecting workers whose occupations require prolonged exposure to cooking-related emissions.

Commercial food vending represents an important source of livelihood and contributes substantially to food access in urban communities, but the occupation may expose vendors to environmental and occupational hazards. Food vendors may spend several hours each day preparing meals, frying foods, boiling ingredients, grilling meat, roasting food and repeatedly heating cooking oils. These activities can generate smoke, particulate matter, gases and cooking fumes, particularly when fuel combustion is incomplete or ventilation is inadequate. A study of occupational cooks found that cooking emissions constitute an important source of fine particulate matter and that cooking fumes can expose workers to pollutants generated during high-temperature food preparation. Similarly, research on commercial kitchens has shown that cooking produces particulate matter and volatile organic compounds, with ventilation playing an important role in determining the level of exposure experienced by kitchen workers. These findings indicate that food preparation is not only a food-safety activity but can also constitute an occupational exposure environment with implications for workers’ respiratory health.

The type of cooking fuel used by commercial food vendors is an important determinant of the pollutants generated during food preparation. Fuels such as firewood and charcoal can produce substantial quantities of smoke and particulate matter, particularly when used in open fires or inefficient stoves. Liquefied petroleum gas (LPG) and electricity generally produce fewer combustion-related pollutants at the point of use, although the overall exposure environment may still be influenced by ventilation, cooking methods and the repeated heating of oils. WHO (2025) reports that polluting fuels and inefficient cooking technologies generate harmful household air pollution containing fine particles and other pollutants capable of penetrating deep into the lungs. Nigerian evidence also indicates that the use of unclean cooking fuels is associated with elevated indoor PM₂.₅ levels and respiratory symptoms. In a Nigerian suburban community, PM₂.₅ concentrations were higher in households using unclean fuels, while respiratory symptoms were also more common among some exposed groups. Although household environments differ from commercial food-vending environments, the findings demonstrate the health relevance of cooking-related air pollution in Nigeria.

Respiratory symptoms are among the important health outcomes that may occur following exposure to polluted indoor air. Such symptoms can include cough, phlegm production, wheezing, chest tightness, nasal irritation, throat irritation and shortness of breath. Occupational exposure to cooking fumes has been associated with respiratory symptoms and changes in pulmonary function in studies involving workers exposed to cooking-related emissions. For example, a Nigerian study of workers exposed to wood smoke and cooking-oil fumes reported significantly increased occurrences of chest tightness, nasal congestion, cough and wheezing among exposed workers compared with controls, alongside lower mean FEV₁ and FVC values among the exposed group. These findings are particularly relevant to commercial food vendors because their work may involve repeated and prolonged exposure to smoke and cooking fumes. The evidence suggests that respiratory symptoms among food vendors should be considered within the broader context of occupational exposure rather than viewed solely as isolated individual health complaints.

The ventilation characteristics of food-vending premises constitute another important component of indoor air quality. Adequate ventilation facilitates the removal or dilution of smoke, cooking fumes, heat and other airborne contaminants, whereas poorly ventilated premises can allow pollutants to accumulate within the workers’ breathing zones. Commercial kitchens with effective ventilation have been shown to reduce exposure to cooking emissions, while high-intensity cooking activities can increase particulate matter concentrations when ventilation is insufficient. In recognition of the importance of environmental conditions in food premises, the National Agency for Food and Drug Administration and Control (NAFDAC, 2025) requires suitable and adequate ventilation and lighting in rooms used as food premises and specifies that ventilation systems should be appropriately designed and maintained. Therefore, ventilation is not only an environmental health consideration but also part of the requirements for maintaining appropriate conditions in food premises. For commercial food vendors, the adequacy of windows, doors, exhaust systems, fans, kitchen layout and other ventilation arrangements may influence the concentration of airborne pollutants to which they are exposed.

Knowledge and awareness of the health hazards associated with cooking-related air pollution may also influence the practices adopted by commercial food vendors. Vendors who understand the potential respiratory consequences of prolonged smoke exposure may be more likely to use cleaner fuels, improve ventilation, avoid unnecessary exposure to smoke and adopt other protective practices. However, evidence from Nigeria suggests that awareness of biomass-smoke hazards among commercial food vendors has historically been limited. A study involving 308 commercial food vendors in Benin and Calabar found that 64.4% were not aware that biomass smoke exposure was harmful to human health, while 71.8% were unconcerned about the effects of biomass-fuel fumes on their health. Only 35.7% reported awareness of the harmful effects of biomass smoke exposure, although some respondents identified measures such as cooking in rooms with open doors and windows and using cleaner fuels as possible ways of reducing exposure. These findings highlight the importance of health education and preventive practices among occupational groups regularly exposed to cooking smoke.

The issue is particularly important in Lagos State because of the large urban food-vending economy and the diversity of cooking environments in which commercial food vendors operate. Vendors may prepare food in enclosed shops, roadside structures, market stalls, temporary shelters or semi-open spaces, with substantial differences in fuel type, cooking duration, ventilation and proximity to other sources of air pollution. Recent evidence directly from Lagos provides a particularly important basis for investigating this issue. Oladunjoye, Aluko and Afolabi (2026), in a cross-sectional study of 291 deep-fry food vendors in Lagos, found associations between cooking fuel type and respiratory indicators including morning phlegm and prolonged cough. The study also highlighted the relevance of ventilation and repeated oil heating to occupational exposure among food vendors. However, the study focused specifically on deep-fry vendors, whereas commercial food vending in Ikeja encompasses a wider range of food preparation activities and cooking environments. Consequently, there remains a need to examine indoor air quality and respiratory symptoms among commercial food vendors in Ikeja, Lagos State, with particular attention to cooking fuel, ventilation, duration of exposure and preventive practices.

1.2 Statement of the Problem

Commercial food vending is an important livelihood activity in urban Nigeria, but the occupation may expose vendors to air pollutants generated during cooking. Food vendors can spend many hours close to frying, boiling, grilling or roasting activities, sometimes in spaces where smoke and cooking fumes are not adequately removed. Nigerian evidence has established that workers exposed to wood smoke and cooking-oil fumes can experience respiratory symptoms such as chest tightness, cough, nasal congestion and wheezing, together with measurable changes in lung function. Similarly, recent research among deep-fry food vendors in Lagos found associations between cooking fuel and respiratory indicators. Despite these findings, respiratory health risks associated with the broader commercial food-vending environment remain an important occupational-health concern requiring further investigation.

A second problem concerns the quality of the air within food-vending environments. Indoor air quality can be affected by the type of cooking fuel, intensity of cooking, repeated heating of oil, availability of windows and doors, use of mechanical ventilation and the physical design of the cooking area. WHO guidelines demonstrate that fine particulate matter is harmful to health even at relatively low concentrations, while Nigerian studies have documented elevated PM₂.₅ concentrations in environments where cooking occurs with polluting fuels. However, commercial food vendors may operate in premises that were not originally designed as kitchens and may have limited ventilation facilities. The extent to which food vendors in Ikeja operate under conditions that permit adequate removal of cooking emissions is therefore an important issue that warrants empirical assessment.

A third problem relates to the continued use of cooking practices and fuels that may increase occupational exposure to airborne pollutants. Some commercial food vendors may select particular fuels because of affordability, availability, cooking speed or suitability for specific foods, even when such fuels generate substantial smoke. In addition, vendors may work for long periods and repeatedly heat cooking oil, increasing the duration and intensity of exposure to cooking emissions. Evidence from Nigerian commercial food vendors has shown limited awareness of the health effects of biomass smoke, while recent Lagos research found that fuel type and prolonged cooking-related practices were relevant to respiratory outcomes among deep-fry vendors. The problem is therefore not limited to the existence of pollutants but also involves the behavioural, occupational and environmental factors that may sustain vendors’ exposure to those pollutants.

Finally, there is a need for location-specific evidence on indoor air quality and respiratory symptoms among commercial food vendors in Ikeja. Although studies have examined household air pollution in Nigeria, occupational exposure among food vendors in Lagos and respiratory effects of wood smoke and cooking-oil fumes, evidence specific to the commercial food-vending environment in Ikeja remains limited. The 2026 Lagos study provides valuable recent evidence, but its focus on deep-fry food vendors does not fully represent the diversity of commercial food vendors and cooking environments within Ikeja. There is therefore a need to examine the relationship between indoor air-quality conditions and respiratory symptoms while considering important factors such as cooking fuel, ventilation, duration of daily exposure and awareness or use of protective practices. Evidence from such a study could support occupational-health education, environmental-health monitoring and practical interventions for improving the working conditions of commercial food vendors in Ikeja, Lagos State.

1.3 Purpose of the Study

The general purpose of this study is to examine indoor air quality and respiratory symptoms among commercial food vendors in Ikeja, Lagos State.

Specifically, the study seeks to:

1. determine the relationship between cooking fuel type and respiratory symptoms among commercial food vendors in Ikeja, Lagos State;
2. examine the relationship between ventilation conditions and respiratory symptoms among commercial food vendors in Ikeja, Lagos State;
3. determine the relationship between duration and intensity of cooking exposure and respiratory symptoms among commercial food vendors in Ikeja, Lagos State; and
4. examine the relationship between awareness and preventive practices concerning indoor air pollution and respiratory symptoms among commercial food vendors in Ikeja, Lagos State.

1.4 Research Questions

The following research questions will guide the study:

1. What is the relationship between cooking fuel type and respiratory symptoms among commercial food vendors in Ikeja, Lagos State?
2. What is the relationship between ventilation conditions and respiratory symptoms among commercial food vendors in Ikeja, Lagos State?
3. What is the relationship between duration and intensity of cooking exposure and respiratory symptoms among commercial food vendors in Ikeja, Lagos State?
4. What is the relationship between awareness and preventive practices concerning indoor air pollution and respiratory symptoms among commercial food vendors in Ikeja, Lagos State?

1.5 Research Hypothesis

The following null hypothesis will be tested at the 0.05 level of significance:

H₀: There is no significant relationship between indoor air quality-related factors and respiratory symptoms among commercial food vendors in Ikeja, Lagos State.

1.6 Significance of the Study

The study will be significant to commercial food vendors because it will provide information about the possible respiratory-health implications of their daily cooking environment. The findings may help vendors recognize the importance of cleaner cooking fuels, adequate ventilation, appropriate work practices and reduction of unnecessary exposure to cooking smoke and fumes.

The study will be useful to occupational health practitioners and environmental health officers because it will provide evidence concerning the environmental and occupational conditions under which commercial food vendors work. The findings may assist these professionals in developing health education, workplace assessment and preventive programmes for food vendors.

The study will also benefit government agencies and policymakers, particularly agencies concerned with public health, environmental health, food premises and occupational safety. Evidence from the study may support the implementation and monitoring of appropriate ventilation and environmental-health requirements in commercial food premises. NAFDAC’s 2025 Food Hygiene Regulations specifically require suitable and adequate ventilation in food premises, demonstrating the regulatory relevance of this issue.

The study will be relevant to food-vending associations and market authorities because the findings may help them identify environmental conditions that could increase respiratory exposure among their members. Such organizations may use the findings to promote cleaner cooking fuels, improved ventilation and appropriate health-protection practices.

The study will further be useful to public-health educators by providing evidence that can inform educational campaigns on indoor air pollution, respiratory symptoms and occupational exposure. This is particularly relevant because previous Nigerian research found limited awareness among commercial food vendors concerning the harmful effects of biomass smoke exposure.

Finally, the study will contribute to academic and research knowledge by providing location-specific evidence on indoor air quality and respiratory symptoms among commercial food vendors in Ikeja. It may serve as a reference for future researchers investigating occupational exposure, indoor air pollution, cooking fuels, ventilation and respiratory health among informal and semi-formal workers in Nigeria.

1.7 Scope of the Study

The study focuses on indoor air quality and respiratory symptoms among commercial food vendors in Ikeja, Lagos State.

The study will examine four major dimensions of the independent variable:

• cooking fuel type;
• ventilation conditions;
• duration and intensity of cooking exposure; and
• awareness and preventive practices concerning indoor air pollution.

The dependent variable is respiratory symptoms, which will include symptoms such as cough, phlegm production, wheezing, shortness of breath, chest tightness, nasal irritation and other relevant respiratory complaints experienced by the vendors.

Geographically, the study will be limited to selected commercial food vendors operating within Ikeja Local Government Area of Lagos State. The study will focus on vendors whose occupations involve regular food preparation and cooking activities.

1.8 Operational Definition of Terms

Indoor Air Quality: The physical, chemical and biological characteristics of air within an enclosed or semi-enclosed food-vending environment, particularly in relation to pollutants generated during cooking and other activities.

Indoor Air Pollution: The contamination of air within an enclosed or semi-enclosed environment by harmful substances such as particulate matter, smoke, carbon monoxide, volatile organic compounds and other pollutants.

Commercial Food Vendor: A person who prepares, cooks and/or sells prepared food to consumers as a business or source of livelihood.

Cooking Fuel: The energy source used by a food vendor for preparing food. It may include LPG, electricity, firewood, charcoal, kerosene or other fuels.

Ventilation: The process by which outdoor air enters a food-vending environment and contaminated indoor air, smoke, heat and cooking fumes are removed or diluted.

Respiratory Symptoms: Physical complaints involving the respiratory system, including cough, phlegm, wheezing, shortness of breath, chest tightness, nasal congestion and related symptoms.

Cooking Exposure: The period and intensity during which a food vendor is exposed to smoke, fumes, heat and other emissions generated during food preparation.

Cooking Intensity: The amount and frequency of cooking activity undertaken by a food vendor, including the frequency of frying, grilling, roasting, boiling or other high-temperature cooking processes.

Preventive Practices: Actions taken by food vendors to reduce exposure to indoor air pollutants, including improving ventilation, using cleaner fuels, maintaining cooking equipment and reducing unnecessary exposure to smoke.

Respiratory Health: The condition and functioning of the respiratory system, reflected in the absence or presence of respiratory symptoms and related health complaints.

Commercial Cooking Fumes: Gases, vapours, smoke and particulate emissions generated during commercial food preparation, particularly during frying, grilling, roasting and other high-temperature cooking processes.

Particulate Matter (PM₂.₅): Fine airborne particles with an aerodynamic diameter of 2.5 micrometres or less that can penetrate deeply into the respiratory system. WHO’s 2021 guideline identifies a 24-hour PM₂.₅ air-quality guideline level of 15 µg/m³.

Project – Indoor Air Quality and Respiratory Symptoms among Commercial Food Vendors: A Study of Food Vendors in Ikeja, Lagos State