Heat Stress Cuts Migrant Worker Productivity In India By 10%, Study Finds

Rising heat and humidity have contributed to a nearly 10 per cent decline in productivity among migrant workers in India over the past four decades, according to PTI, which cited a new study by researchers from the Indian Institute of Technology (IIT) Gandhinagar.

Published in the journal Earth’s Future, the study found that between 1980 and 2021, rural-to-urban migration hotspots across northern, eastern, and southern India recorded a significant increase in humidity levels, signalling greater exposure to heat stress, both outdoors and indoors.

Mumbai, Delhi, Kolkata, and Hyderabad were identified as the top four cities with the largest inflow of migrants, with a combined migrant population estimated at up to 10 million, PTI reported.

The researchers warned that with every additional degree of global warming, migrant workers could experience higher heat stress and a reduced ability to carry out physical labour. Migrant workers, who move from rural to urban areas seeking employment, form a large segment of India’s workforce, with studies suggesting they make up 42 per cent of the total population. A 2020 study in The Indian Journal of Labour Economics estimated 450 million internal migrants, based on the 2011 Census.

Engaged primarily in physically demanding outdoor work, many migrant workers face heightened vulnerability to heat stress, a condition where the body fails to regulate its temperature under high heat and humidity. The report noted that climate change has intensified this risk, leading to reduced productivity and income among outdoor labourers.

The study also projected that the duration of extreme heat stress seasons will continue to increase, posing further challenges to the health and work capacity of migrant workers. “We show that during 1980–2021, most rural-to-urban migration hotspots in north, east, and southern India witnessed a significant rise in (wet bulb temperature), indicating (an) elevated indoor heat stress,” the authors wrote. “Over that interval, outdoor heat stress has considerably increased and led to a (nearly) 10 per cent decline in labour capacity in these hotspots,” they added.

The team analysed data from the 2011 Census and global climate models, focusing on 50 major Indian cities where residents have limited options to avoid heat exposure.

The projections indicate that almost all urban regions could face high indoor heat stress if global temperatures rise beyond 2°C above pre-industrial levels. Under scenarios of 3°C and 4°C warming, typical labour capacity could drop to 71 per cent and 62 per cent respectively, compared with 86 per cent if current trends continue.

According to PTI, the researchers also noted that outdoor workers performing moderate or heavy tasks in Chennai and parts of West Bengal could face productivity losses of up to 35 per cent when wet bulb temperatures exceed 28°C.

The findings underscore the growing challenge climate change poses to India’s urban workforce and the need for stronger adaptation measures to protect those most exposed to rising heat.

(With inputs from PTI)