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Exploring indoor air pollution in Nigeria


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Exploring indoor air pollution in Nigeria

oforiSandra Ofori is a climate researcher and environmentalist based at the University of Port Harcourt in Nigeria, and a CIRCLE Visiting Fellow at the University of Ghana in Accra, Ghana. The Climate Impacts Research Capacity and Leadership Enhancement (CIRCLE) Fellowship is a post-doctoral fellowship scheme, that aims to develop the skills and research results of African early career researchers in the field of climate change. CIRCLE is implemented through the AESA Platform. AESA (The Alliance for Accelerating Excellence in Science in Africa) is a funding, agenda-setting, programme management initiative of  the African Academy of Sciences (AAS) in partnership with the African Union Development Agency (AUDA-NEPAD), founding and funding global partners, and through a resolution of the summit of African Union Heads of Governments. CIRCLE is supported by the Association of Commonwealth Universities (ACU). CIRCLE is is supported by the Association of Commonwealth Universities (ACU).


According to the WHO, illnesses attributable to indoor air pollution contribute to almost four million premature deaths globally, with most deaths occurring in low- and middle-income countries. Sandra Ofori’s project illustrates that indoor air pollution from biomass fuels is associated with evidence of cardiovascular and respiratory disease in Nigeria.


Indoor air pollution (IAP) refers to the chemical, biological and physical contaminants in the air inside a building. Among potential air pollutants, those that are detrimental to human health include particulate matter (PM), carbon monoxide, nitrogen dioxide (NO2), Sulphur dioxide (SO2) and the carcinogen benzo(a)pyrene. Particles that are 10 μm in diameter or smaller are dangerous, particularly those below 2.5 μm (PM2.5), because they can enter the lungs through the airways and contribute to cardiopulmonary disease through various mechanisms. Different studies from around the world have linked indoor air pollution to recurrent respiratory illness that exacerbates asthma – keeping children away from school --, chronic obstructive airway disease, hypertension, cardiovascular disease and even death from ischemic heart disease and stroke. Yet the use of biomass remains prevalent, especially in rural areas.

The social and economic development of a region is closely related to determinants of indoor air pollution. For instance, in developing countries, indoor air pollution results from the use of biomass fuels (which likely reflects energy poverty), while in industrialised countries, the use of chemicals such as insecticides and formaldehyde increase indoor air pollution. Worldwide, the main contributor to indoor air pollution is the combustion of biomass fuel for heating, cooking and other domestic uses. Hazardous gases are released from incomplete combustion of these solid biomass fuels. In much of the developing world, cooking for the home is the job of the woman, who are also the caregivers of young children and have their children around them when they cook. Thus, women and young children are most vulnerable to the effect of indoor air pollution due to their close proximity to home fires.

This study examines the association between exposure to biomass gases and subclinical cardiovascular and respiratory disease in adults living in rural communities. At the time of the study period, there was no published research on this association in Nigeria.

Description of study

The study was conducted in rural farming communities in Rivers State, a farming state selected because it is one of six states in the Niger-Delta region of Nigeria. The area has a rich basin of crude oil and natural gas. Exploration activities over the years have led to massive environmental pollution (air and water). Because Rivers State is made up of 23 local government areas (LGA), we started with a multi-stage sampling framework to select a predominantly rural LGA with no oil or gas exploratory activities. This approach was to avoid confounding the effects of significant ambient air pollution with indoor air pollution. We furthermore chose this LGA because it also suffers from considerable energy poverty and ample availability of wood fuel, together assuring the prevalence of individuals exposed to indoor air pollution from biomass fuel use.

The LGA consists of nine communities; simple random sampling techniques were employed to select three (Omelema, Emilaghan and Ogbema). From each of these communities, at least 128 households were sampled. The first household was selected by simple random sampling; subsequently, every third household was sampled. Data was collected from one eligible participant per household who self-identified as the principal cook for that household until the sample size was achieved. Where selected households did not have eligible participants, the next eligible household was used. Standard questionnaires were used to collect demographic, fuel use and respiratory disease data from the participants.

A Metone Aerocet 531 automatic instrument was used to measure indoor air pollutants and a portable ultrasound machine to noninvasively measure the thickness of the inner layer of participants’ carotid arteries, big blood vessels that take blood to the brain from the heart. The inner layer of a healthy carotid artery is thin and smooth. The carotid artery carries blood from the heart to the brain. When there is inflammation, the inner layer thickens and can bulge inwards due to the build-up of plaque. This can narrow the vessel, reducing the flow of blood to the brain, which may cause stroke. Thickening of this inner layer usually occurs many years before a clinical event like a stroke; measuring its thickness can detect subclinical underlying cardiovascular disease. We also measured the blood pressure of participants and used a portable peak flow meter, a crude measure of large airway function, to measure peak expiratory flow rates. A total of 389 women who self-identified as principal cooks in the home were included in the study.


We found that most of the women in the rural areas studied use biomass fuel over other energy source (kerosene, liquified petroleum gas or electricity) and that its use is associated with lower peak expiratory flow rates (a surrogate marker of large airway obstructive disease), higher blood pressure and thicker inner carotid artery walls. The use of biomass is used as the predominant source of fuel because ample wood from farms is freely available, cheap and familiar. Cleaner energy sources like liquified petroleum gas is expensive and not readily available. Discussion with some of the participants at a town hall event held by the researchers to engage the community in the study revealed other nuanced reasons for using wood for fuel: the taste of biomass fuel-cooked food, fear of gas explosions and unconscious biases, such as the belief that gas is to be reserved for special occasions or for only educated people. Both cause and effect were at play because more educated people tended to use cleaner energy sources, and thus cleaner energy sources tended to be perceived as the domain of the more educated, even within the same community.

These results are important because the adverse associations between the use of biomass fuels and signs of underlying cardiovascular and respiratory problems is pronounced and alarming. Countries like Nigeria are undergoing epidemiologic transition, facing the dual burden of communicable and non-communicable disease. The focus of public health officials in addressing cardiovascular and chronic respiratory disease prevention tends to be on reducing risk factors like cigarette smoking, sedentary lifestyle and obesity. However, little attention is paid to indoor air pollution, which is a significant contributor to these problems in settings like Nigeria and likely many other African countries.

Involving key stakeholders, including local government chairmen, local health representatives and the state commissioner of health, from the beginning of the study was critical to the outcome, as was the presentation of findings to study participants and other members of the communities through town hall meetings.

Several potential strategies can mitigate the adverse effect of smoke exposure. The provision of cleaner cooking fuels, and/or more energy-efficient cook stoves with expulsive chimney hoods, will reduce the levels of harmful air pollutants released, especially indoors, during combustion. Education about the need for properly ventilated kitchens to reduce exposure is necessary. These require concerted governmental efforts and campaigns to make cleaner fuels and cookstoves available to a large portion of the vulnerable population. More importantly, understanding the reasons for the fuel use patterns in these communities through well-designed qualitative studies will allow the implementation of solutions that will be culturally acceptable and thus effective.


It was clear in the course of this study that in climate change research, more collaboration is needed among the medical community, public health officials and climate change scientists.

There is more work to be done to study the impact of Indoor air pollution on the cardiovascular and respiratory health of the population and adaptation methods that can be employed to protect human health. Also, it became obvious over the course of the study that scientists also have to be advocates for change. At one town hall meeting, an elderly member of the community asserted, “now [that] you have told us that our way of life is causing us problems, what are we supposed to do?” I had no answer because I could not provide cleaner alternative fuels to them. Advocacy to key decision makers and politicians is key if research is to result in real change to the health of the community. Further research in this area needs to focus on the best methods to provide sustainable sources of alternative fuels in these communities.


This project has shown that indoor air pollution from biomass fuels is associated with subclinical evidence of cardiovascular and respiratory disease in the community. Previous research demonstrated the impact of indoor air pollution on acute respiratory and cardiovascular events. We have shown that even in the absence of acute events, subclinical damage that may add to the burden of long-term morbidity occurs with exposure.

Although it was outside the study scope to provide alternate sources of fuels to the community, researchers engaged the community to teach about the dangers of indoor air pollution and the importance of outdoor kitchens with proper ventilation to reduce adverse impacts. Illustrated flyers were distributed to help reinforce messaging. Findings from this study were published as two articles in peer-reviewed journals. Recommendations were made to the state ministries of health and environment on the need to provide sustainable sources of cleaner fuels for rural communities and more efficient cookstoves that can burn biomass more efficiently and therefore release less particulate matter and other noxious gases into the atmosphere.