Study: Men walking on roads inhaling highest toxic air levels

It attributed this difference to multiple factors, “including gender, age, particle size, airway morphology, and breathing parameters such as tidal volume, inhalation/ exhalation duration, and breathing frequency”.

A new five-year study has flagged that exposure to pollution varies by gender, the type of physical activity and time of day, with men walking along Delhi’s roadsides inhaling the highest doses of toxic air.

Rashtrapati Bhavan shrouded in dense winter fog on Sunday morning. (Sanjeev Verma/HT Photo)

The study, carried out by Netaji Subhas University of Technology analysed particulate pollution data between 2019 and 2023 to calculate the respiratory deposition doses (RDD), the amount of particulate matter that actually settles in the lungs. It was published in the peer-reviewed Nature journal on November 28.

Titled Respiratory Deposition of Particulate Matter in Delhi: A Five-Year Assessment of Exposure Patterns and Health Risks, the research was carried out in collaboration with Noida-based environmental consultancy, AARC Engineers and Consultants India Pvt Ltd, andused Central Pollution Control Board (CPCB) data on PM 2.5 and PM 10 to estimate RDDs for adult men and women at both 15-minute and daily intervals.

The assessment examined two activity scenarios — sitting and walking — across morning and evening commuting hours, focusing on working adults and students. It found that men walking along Delhi’s roadsides – especially during the evening commute are inhaling significantly higher doses of the city’s toxic air than women.

It attributed this difference to multiple factors, “including gender, age, particle size, airway morphology, and breathing parameters such as tidal volume, inhalation/ exhalation duration, and breathing frequency”.

The study further found that RDD values for PM2.5 were highest in industrial areas, followed by commercial, institutional, and then residential regions. “In the sitting position, male RDDs were 1.4 times higher than those for females; during walking, males’ RDDs were 1.2 times higher than females. Across all respiratory regions, RDDs were greater during walking than sitting,” it said.

In industrial regions, the maximum daily total RDD for PM 2.5 was recorded at 13.13 µg/min for walking men, compared with 10.92 µg/min for walking women, 4.73 µg/min for men sitting, and 3.38 µg/min for women sitting — all observed in 2019, data showed.

A similar pattern emerged for PM10, which are larger and coarser particles. The highest deposition occurred among men who were walking, followed by women walking, men sitting and women sitting. The maximum daily PM 10 RDD reached 15.73 µg/min for walking men, compared with 13.64 µg/min for walking women, 5.66 µg/min for men sitting and 4.22 µg/min for women sitting. Notably, walking-related RDDs were substantially higher than sitting levels—2.78 times higher for men and 3.23 times higher for women.

Meanwhile, central Delhi – characterised by government offices, residential neighbourhoods and overall greenery, showed comparatively lower exposure levels, further highlighting the disproportionate pollution burden borne by workers, roadside vendors and daily wage earners who spend long hours outdoors.

The study warned that male walking RDD values were between 10 and 40 times higher than doses calculated at National Ambient Air Quality Standards (NAAQS) and World Health Organization (WHO) guideline levels, a range that could have severe implications for lung health. High RDDs are closely linked to the onset and progression of respiratory illnesses such as asthma and chronic obstructive pulmonary disease (COPD), the researchers said.

Dr Vikas Maurya, Senior Director and Head, Pulmonology at Fortis Hospital in Shalimar Bagh told HT that the study underlines two known factors — increased physical activity increases the inhalation rate and that typically men are involved in higher physical activities. “Men also have larger lungs so typically, they are able to inhale more air. With an increase in physical activity, this only increases further so the breathing rate increases depending on the nature of activity. Additionally, we see men outdoors for longer too so their exposure overall is also higher,” he said.

The data further showed persistent regulatory breaches. The NAAQS daily limit for PM 10 (100 µg/m³) was exceeded on an average 77.5% of days during the five-year period, while the WHO guideline of 45 µg/m³ was breached on 96.5% of days. For PM 2.5, both the NAAQS standard (60 µg/m³) and the WHO guideline (15 µg/m³) were exceeded almost continuously