Some men decided the air was safe

In December, Delhi struggled to breathe as nitrogen dioxide (NO₂) levels averaged 47 micrograms per cubic metre. More than the 40 micrograms limit that the WHO set in 2009, and over four times more than its revised 2021 limit of 10 micrograms per cubic metre. The levels, however, were well within India’s 80 micrograms per cubic metre benchmark — a number that has not been revised since 2009. Delhi is among the thousands of cities across India battling different grades of air pollution.

The scientists and bureaucrats behind India’s standard worked within the frameworks inherited from Western industrial-era research. The default model for these frameworks was the adult male, approximately 70 kilogrammes, engaged in moderate physical activity. The standard for safe air was set by men who would never have to go through pregnancy.

NO₂ exposure, even at levels above roughly 26 micrograms per cubic metre, can reduce the number of eggs a woman carries and disrupt the menstrual cycle. Sulphur dioxide (SO₂), another pollutant, generates oxidative stress in the tissue it contacts. In the uterus, this causes endometrial inflammation. The lining that must receive and sustain a fertilised embryo is rendered hostile towards it. Systematic reviews across Asia, Europe, and North America, have found that SO₂ exposure during pregnancy is consistently associated with low birth weight. The associations between particulate matter and spontaneous abortion are similarly strong across populations.

A district-level study linking satellite-derived PM2.5 data with NFHS-5 maternal health indicators found that a 10 microgram per cubic metre increase during pregnancy raised the risk of low birth weight by 5% and preterm birth by 12%, with the upper Gangetic plain emerging as particularly vulnerable. About 13% of children in the national sample were born preterm; and 17% were underweight. India accounts for roughly 40% of global low birthweights. These outcomes have often been framed as development challenges — but they are also air quality challenges.

Rising temperatures intensify the problem. During heatwaves pollutants are trapped closer to the ground. Women working outdoors in agriculture, construction, roadside vending, and brick kilns experience heightened exposure precisely when their bodies are already under physiological stress. Yet none of this is accounted for in current regulatory thinking.

The standards declared the air acceptable. The outcomes suggest otherwise. We must ask: Who gets to decide what is safe? Who bears the cost when the decision is wrong? If the answer to the first is mostly men, and to the second is women with unacknowledged losses — we must acknowledge that our standards and regulatory procedures are wrong.

Environmental Impact Assessments are not required to capture these outcomes. The health modelling for the construction of a thermal plant or industrial estate is not sex-disaggregated. It does not model foetal exposure windows — the critical 4-to-8-week period of cardiac development, the 8-to-12-week window of neural tube formation — against the pollution plume of the proposed facility. Thus, the clearance is granted based on a standard that was only built on men’s body.

Our regulatory imagination must catch up with our scientific knowledge and the experience of women whose bodies have been silently absorbing the cost of our industrial ambitions for decades.

India's National Ambient Air Quality Standards for NO₂ and SO₂ should be revised to reflect the WHO's 2021 guidelines, with a specific provision for ambient concentrations in zones with high proportions of outdoor female workers and reproductive-age women. Sex-disaggregated reproductive health impact assessments must become a mandatory component of industrial environmental clearances. Investments must be made AI-driven tools to generate reproductive vulnerability scores for all districts in India. The recommendations should be made available to and put that information in the hands of the ASHA workers and antenatal care providers.

Every World Environment Day attention rightly turns to forests and rivers. Yet there is another ecology that demands recognition — the uterus. It too is an environment. It too is under threat. And it too deserves a standard built with it in mind. If the standards do not move with science, the gap can only be measured in miscarriages, and in children lost.

Angela Chaudhuri is CEO of Swasti, a public health nonprofit.

(Disclaimer: The views expressed above are the author's own. They do not necessarily reflect the views of DH).