A recent study conducted by researchers from Delhi Technological University (DTU) and IIT-Delhi has revealed that the air inside kitchens can be as polluted, and often even more toxic, than the air outside. The research, led by Dr Rajeev Kumar Mishra and research scholar Monika Sharma from DTU's advanced air and acoustics research laboratory, along with Prof Mukesh Khare of IIT-Delhi, assessed indoor air quality in households across four income groups in north Delhi's GTB Nagar.
Study Methodology and Key Findings
The study monitored kitchens and bedrooms of urban poor, low-income, middle-income, and high-income households during winter, summer, and monsoon seasons. Kitchens emerged as the most polluted space across nearly all categories, irrespective of income levels. Average PM2.5 concentrations in kitchens ranged between 60 and 100 micrograms per cubic metre (µg/m3), while PM10 levels ranged from 115 to 145 µg/m3, significantly exceeding the safe limits recommended by global health agencies.
Seasonal Variations and Pollution Peaks
During winter, PM10 concentrations peaked at nearly 250 µg/m3 in kitchens and 200 µg/m3 in bedrooms. The study found that poorly ventilated kitchens recorded the highest concentrations: PM10 at 247 µg/m3, PM2.5 at 200 µg/m3, and PM1 at 153 µg/m3. PM1 contributed approximately 40% to 85% of PM10, indicating a high proportion of ultrafine particles.
Sources of Indoor Pollution
The study, published in the journal Particulate Science and Technology, linked indoor pollution strongly to daily household chores. Cooking, especially during breakfast and dinner, caused sharp spikes in particulate matter levels. Poor ventilation, attached kitchens, long cooking times, and lack of exhaust systems further worsened indoor air quality. Even in affluent homes with modern infrastructure, indoor pollution remained high due to activities such as burning incense, dusting, and inadequate ventilation during winters, according to Dr Mishra.
Impact of Housing Inequality
The research provides a stark snapshot of Delhi's housing inequality. In urban poor and low-income households, cramped layouts and the absence of separate kitchens allowed pollution to spread rapidly throughout the house. Many of these homes lack windows or exhaust systems, trapping smoke and fine particles indoors for hours.
Health Risks and Vulnerable Populations
Researchers noted that PM1, extremely fine particles capable of penetrating deep into the lungs, formed a large proportion of indoor pollution, contributing nearly 70% to 80% of PM10 in several houses. Women, children, and elderly residents were identified as the most vulnerable because they spend considerable time indoors. Exposure modelling showed that PM2.5 particles were heavily deposited in the lower lungs, increasing long-term risks of respiratory and cardiovascular diseases. Adults exhibited the highest exposure due to higher breathing rates, while children faced elevated risks because of developing lungs.
Call for Policy Interventions
The study presses for policy interventions, including the need for indoor air quality guidelines, improved ventilation standards in houses, public awareness campaigns, and affordable mitigation measures for low-income communities. Dr Mishra emphasized that Delhi's air pollution debate has focused overwhelmingly on outdoor emissions while neglecting indoor environments, where people spend nearly 90% of their time.
