In
rural Nepal, during the morning cooking hour, the particulate matter
concentration near a traditional biomass cookstove measures approximately 1,376
micrograms per cubic metre of air (PMC, Nepal Cookstove Intervention Trial).
The WHO's air quality guideline for fine particulate matter, PM2.5, is 15
micrograms per cubic metre averaged over twenty-four hours. The woman cooking
the morning meal for her family is breathing air that exceeds the WHO safety
threshold by a factor of more than ninety. Her infant, carried on her back, is
breathing the same air. The kitchen she is standing in does not appear in any
national air quality monitoring report. It is not measured by the satellite
instruments that generate the data maps that policymakers use to understand air
pollution in South Asia. It does not register in the outdoor PM2.5 readings
that generate newspaper headlines and urban policy conversations. It simply
fills the room. It fills her lungs. And it fills the lungs of her children,
morning after morning, across millions of households, across Nepal, India,
Bangladesh, Pakistan, and Sri Lanka, without producing the public health
response that its mortality burden unambiguously demands.
The
myth that air pollution is an outdoor urban problem, something that happens on
congested roads and in industrial districts, is not simply a popular
misunderstanding. It is a policy failure with a body count. The most
methodologically current estimate comes from the Global Burden of Disease Study
2021, published in The Lancet in 2024, which documented 3.1 million deaths
attributable to household air pollution in 2021 alone, with South Asia
accounting for 36 percent of that global mortality, a larger share than any
other region on earth (GBD 2021 Household Air Pollution Collaborators, The
Lancet, 2024). This figure sits close to the WHO's long-standing fact sheet
estimate of 3.8 million annual deaths, a number drawn from earlier modelling
years and a marginally different set of disease endpoints; the two estimates
are not contradictory, but rather successive generations of the same underlying
calculation, and this article uses the more recent GBD 2021 figure as its
primary reference throughout. These deaths are not statistical abstractions.
They are the accumulated consequence of a daily exposure that the people most
affected do not recognise as dangerous, that the healthcare systems they access
do not routinely diagnose as occupationally or environmentally caused, and that
the policymakers who govern them have not addressed with anything approaching
the urgency the evidence demands.
What Is Actually in
the Air
The
combustion of solid fuels, including firewood, crop residue, animal dung, coal,
and charcoal, in open fires and poorly ventilated traditional cookstoves
produces a complex mixture of health-damaging pollutants. These include fine
particulate matter at concentrations far exceeding outdoor ambient levels,
carbon monoxide, sulphur dioxide, nitrogen oxides, benzene, formaldehyde,
polycyclic aromatic hydrocarbons, and a range of volatile organic compounds.
Several of these compounds are classified by the International Agency for
Research on Cancer as Group 1 human carcinogens. The fine particulate fraction,
specifically PM2.5, is the most clinically significant component because
particles of this size penetrate the lung parenchyma, enter the bloodstream, and
reach organs beyond the respiratory system, including the heart, brain, and
placenta (WHO, 2025).
In
Nepal, a nationally representative study published in BMC Public Health found
that twenty-four-hour average indoor PM concentrations in households using
solid fuels, even in kitchens located outside the main house, exceeded both
Nepal's national indoor air quality standards and the WHO PM2.5 guidelines
(Ghimire et al., BMC Public Health, 2019). A separate analysis of rural
households in southern Nepal measured average PM2.5 concentrations near
traditional cookstoves at 1,376 micrograms per cubic metre during cooking
periods, with carbon monoxide levels averaging 10.9 parts per million, a
concentration associated with acute poisoning at sustained exposure (PMC, Nepal
Cookstove Intervention Trial). These are not peak exposure measurements
recorded under exceptional conditions. They are what women in rural Nepal
breathe during the ordinary act of preparing food for their families.
More
than half of Nepalese households, an estimated 54 to 60 percent nationally
according to recent government and World Bank data, still depend on unprocessed
traditional biomass, including firewood, animal dung, and agricultural residue,
as their primary cooking fuel, with the figure rising above 80 percent in rural
areas (Nepal National Planning Commission, 2024, cited in Household Cooking in
Nepal: An Economic Analysis, ScienceDirect, 2026; World Bank Development
Indicators, 2022). Women in these households are exposed to indoor cooking
smoke for a minimum of six hours per day (ResearchGate, Consequence of Indoor
Air Pollution in Rural Area of Nepal, 2015). They do not describe this exposure
as an occupational hazard. They do not report it to a clinician as a risk
factor. They experience the chronic cough, the breathlessness, the diminished
exercise tolerance, and the recurrent respiratory infections that result from
it as ordinary features of life, unremarkable because they are universal in
their communities, and because no one has told them that these features are
caused by what they inhale every morning.
The Disease Burden:
Far Beyond the Lungs
The
clinical consequences of chronic household air pollution exposure extend well
beyond the respiratory diseases most commonly associated with it. The
documented disease associations include chronic obstructive pulmonary disease,
lung cancer, ischaemic heart disease, stroke, pneumonia, pulmonary
tuberculosis, nasopharyngeal and laryngeal cancer, cataracts, low birth weight,
increased infant and perinatal mortality, and stunted childhood development
(The New Humanitarian, Nepal, 2023). A 2025 study published in The Lancet
Regional Health Southeast Asia found that women using polluting cooking
fuels in rural Karnataka, India, showed measurably poorer cognitive performance
compared to women using cleaner fuels, with neuroimaging evidence suggesting
structural brain changes consistent with those documented in ambient air
pollution studies (The Lancet Regional Health Southeast Asia, 2025). Polluting
cooking technology users demonstrated elevated risk of cognitive impairment,
with rural women, the population most exposed, identified as particularly
vulnerable to household air pollution's effects on the brain.
The
cardiovascular consequences are equally significant and equally invisible in
South Asian clinical settings. A national and provincial estimation study,
drawing on Nepal's 2019 Multiple Indicator Cluster Survey data and published in
the Nepalese Journal of Statistics, found that the attributable burden of COPD
and asthma linked to household air pollution reached 63.6 cases per 1,000
population nationally, with attributable fractions found to be 1.3 to 1.5 times
higher in rural Nepal than in urban areas, and with Karnali province, one of
the country's poorest and most biomass-dependent regions, identified as the
worst affected, carrying attributable fractions between 45.3 and 65.6 percent
of its total respiratory disease burden (Shrestha, Nepalese Journal of
Statistics, 2022). Chronic obstructive pulmonary disease is highly prevalent in
Nepal at the community level and is systematically underdiagnosed, particularly
among elderly, illiterate, and rural women, precisely the population with the
highest lifetime biomass smoke exposure, and a national systematic review found
the prevalence of airflow obstruction was significantly higher among rural
dwellers and biomass fuel users than among liquefied petroleum gas users (PMC,
The Burden of Chronic Respiratory Diseases in Adults in Nepal, 2021).
For
infants and young children, the consequences are compounded by physiology. An
infant's air intake is approximately twice that of an adult per unit of body
weight, and infants spend more time indoors than any other demographic group,
maximising their proportional exposure to indoor pollutants. Exposure to
firewood smoke in poorly ventilated conditions has been associated with a
greater than one hundred percent increase in the risk of acute respiratory
infections in young children, as well as associations with low birth weight,
pulmonary tuberculosis, laryngeal cancer, and cataracts in longitudinal studies
(The New Humanitarian, 2023). The child carried on the back of the woman
cooking over an open fire is not an incidental bystander to her occupational exposure.
The child is a primary victim of it.
Incense: The Invisible
Contributor Nobody Discusses
The
public health conversation about indoor air pollution in South Asia, to the
limited extent that it occurs at all, focuses almost entirely on cooking fuels.
It almost never addresses incense burning, despite the fact that incense is
burned daily across hundreds of millions of South Asian homes for religious,
cultural, and aesthetic purposes, and despite the fact that the evidence for
its health effects is substantial and growing. A peer-reviewed analysis
documented that incense sticks release almost five times as much particulate
matter per unit weight burned as cigarettes (FLAME University, 2023). The
particulate matter produced by incense combustion includes polycyclic aromatic
hydrocarbons, benzene, toluene, and carbonyl compounds, several of which are
classified as known or probable human carcinogens.
The
clinical evidence linking incense burning to adverse health outcomes includes
associations with cardiopulmonary morbidity and mortality, wheeze and
respiratory symptoms in children, cognitive impairment and altered brain
functional connectivity in older adults, ADHD-like symptoms in children exposed
to incense smoke, and an increased prevalence of prediabetes and Type 2
diabetes mellitus in populations with chronic occupational incense exposure
(Scientific Reports, 2020; Pakistan Journal of Medical Sciences, 2022). A
systematic review found that almost all studies examining the relationship
between indoor air pollution and adult cognition identified a positive
association between exposure and cognitive dysfunction, with elderly women
identified as most susceptible. In the context of South Asia's approaching
dementia epidemic, this finding is not academic. It is a preview of an
avoidable cognitive disease burden accumulating in communities where incense
burning is a daily devotional practice and where no clinician has ever asked
about it as a health exposure.
The
WHO's fact sheet on household air pollution does not separately address incense
burning as a category of indoor air pollution requiring clinical or policy
attention. National action plans for air quality improvement in South Asian
countries do not address incense burning. Clinicians conducting respiratory or
cognitive assessments in South Asian primary care settings do not routinely ask
patients whether they burn incense daily and for how long. The evidence that
this question matters has been available for more than a decade. The clinical
systems that could act on it have not.
Who Bears the Burden
and Why This Is a Gender Issue
The
WHO has explicitly recognised household air pollution as a gender issue. In its
widely cited 2012 estimate, women and children accounted for more than sixty
percent of all premature deaths from indoor air pollution globally, a disparity
driven by a straightforward structural reason: in South Asia, cooking is
overwhelmingly women's work. Women in rural Nepal spend more than five hours
within two metres of the cooking stove each day. They are the closest and most
prolonged point of exposure to the pollutants the stove produces. They are
also, in many cases, the family members least likely to have their respiratory
symptoms attributed to an environmental cause, least likely to receive a formal
COPD diagnosis, and least likely to be considered occupationally exposed to a
harmful substance, because the kitchen is not classified as a workplace and
cooking is not classified as an occupational exposure in most South Asian
regulatory or clinical frameworks (ICIMOD, The Gendered Impacts of Indoor Air
Pollution in Nepal's Koshi Basin, 2021).
The
consequence of this structural invisibility is that a woman who has spent
thirty years cooking over a biomass fire presents to a primary care clinic with
dyspnoea, chronic cough, and diminished exercise tolerance and is assessed
without any inquiry into her household fuel use. Her symptoms are attributed to
ageing, to prior tuberculosis, or to causes that require investigation for
which neither she nor the health system has resources. The COPD that her
cooking exposure has produced over three decades is not diagnosed. It is not
treated. It is not counted in any occupational disease register because no
register acknowledges that her kitchen was the workplace that made her ill.
A 2025
systematic scoping review published in the Journal of Family Medicine and
Primary Care, examining perceptions of solid biomass fuel use across South
Asian countries, found that over half of the world's population continues to
cook using solid fuels, that 47 percent of families globally have not
transitioned to cleaner cooking technologies despite progress toward universal
access, and that physicians and primary care providers are critically
underutilised in addressing household air pollution, with environmental health
counselling almost entirely absent from routine clinical encounters (Journal of
Family Medicine and Primary Care, 2025). The review explicitly identified
primary care practitioners as a neglected but strategically positioned resource
for behaviour change, given that they see the patients most affected and are
positioned to ask the questions that no other system is currently asking.
The Policy Gap: What
Is Not Being Done
South
Asian governments have invested significantly in monitoring, reporting, and
generating policy responses to outdoor ambient air pollution over the past
decade. The AQI readings that appear on smartphone screens and news broadcasts
across Kathmandu, Delhi, Dhaka, and Karachi measure outdoor PM2.5. The
monitoring stations that generate them are placed in urban centres. The policy
conversations they produce focus on vehicle emissions standards, industrial
regulation, crop burning bans, and construction dust management. None of this
is wrong. Outdoor air pollution in South Asian cities is genuinely catastrophic
and deserves every instrument of policy it is receiving.
What
it does not deserve is to serve as the exclusive framing for air quality as a
public health issue in a region where the majority of air pollution deaths are
caused not by outdoor exposure but by the kitchen fire. A woman in a rural
Nepali village does not benefit from improved outdoor AQI in Kathmandu. She
benefits from a clean cookstove, an improved kitchen ventilation system, access
to LPG or electricity for cooking, and a primary care clinician who asks her
what fuel she uses to cook and documents it as a clinical exposure in her
health record. These interventions are technically available, increasingly
cost-effective, and proven to reduce both emissions and health burden in
multiple intervention trials. They remain inadequately funded, inadequately
distributed, and inadequately integrated into the national health system
responses of every South Asian country.
The
Pradhan Mantri Ujjwala Yojana in India, launched in 2016, represents the most
significant governmental attempt in the region to address household fuel
transition at scale, providing subsidised LPG connections to low-income
households. It reached over ninety million households. Studies on its health
impact are ongoing and mixed, partly because LPG connection does not always
translate into sustained LPG use due to refill costs, and partly because many
beneficiary households continued using biomass in parallel. The lesson from its
implementation is not that fuel transition programmes are ineffective. It is
that they require sustained subsidy to remain economically accessible to the
lowest-income households, that they must be accompanied by behaviour change
support, and that their health impact requires monitoring through clinical
systems that currently do not ask the right questions.
Conclusion: The Air
Inside the Home Is a Clinical and Policy Responsibility
The
3.1 million people who died from household air pollution in 2021 did not die
from a pathogen, a genetic susceptibility, or a condition that medicine cannot
address. They died from a daily exposure to a toxic substance produced in their
own homes, by the fuel they used to cook their food, in an indoor environment
that no monitoring system measured, that no clinical guideline prompted their
doctors to ask about, and that no policy framework classified as an
occupational or environmental health emergency requiring urgent intervention.
South Asia carried 36 percent of that global mortality. The majority of the
people who constituted that statistic were women and children.
Policymakers
and health professionals reading this article operate in systems that have, for
structural and cultural reasons, consistently underestimated indoor air
pollution as a public health priority. The measurement systems are oriented
toward outdoors. The clinical training does not prompt environmental exposure
histories. The regulatory frameworks do not classify the kitchen as a hazardous
workspace. The funding allocations for clean energy transition programmes are
insufficient relative to the scale of the health benefit they would deliver if
fully implemented. All of these are correctable failures, and all of them
require corrective decisions that lie within the professional and institutional
authority of the people this article addresses.
The
WHO has called household air pollution the world's largest single environmental
health risk. It has been saying this, in various forms, for more than two
decades. The South Asian woman standing at her cookstove for six hours each day
did not need the WHO to tell her that the smoke bothered her eyes, or that she
coughed every morning, or that her children seemed to get chest infections more
than other children she knew. She already knew something was wrong. She did not
know that it had a name, that it was preventable, and that the institutions
responsible for her health had the evidence, and the obligation, to act on it
long before now.
