‘SRA designs curb air flow, worsen indoor air pollution’

The recent study, which reveals the indoor air pollution in Slum Rehabilitation Authority (SRA) homes in the city is five times the national limit, points to the need to revise the design policy for the buildings.

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The research was carried out by a four-member team led by professor Ronita Bardhan from Indian Institute of Technology (IIT) – Bombay, India (now at University of Cambridge, UK) and Professor Leslie Norford from Massachusetts Institute of Technology, USA.

Researchers found that the air quality inside SRA buildings was below average, in part due to lack of ventilation and poor interior design. The study, ‘Indoor air quality among Mumbai’s resettled populations: Comparing Dharavi slum to nearby rehabilitation sites’, was undertaken at Natwar Parekh in Govandi, constructed in 2008; Lallubhai Compound in Mankhurd, constructed in 2003, and 18 Dharavi dwellings.

Natwar Parekh contains 4,800 dwellings across 50 tenements while Lallubhai Compound comprises 9,300 dwellings across 65 tenements.

Air quality levels measured in the foyer, kitchen and sleeping area in these SRA houses exceeded average particulate matter (PM) 2.5 levels recorded in the entire slum household. As against the average PM2.5 level of 118ug/m3 (micrograms per cubic metre) in slum dwellings at Dharavi, the average PM2.5 level in the foyer, kitchen and sleeping areas at Natwar Parekh stood at 305, 326, and 192 μg/m3, respectively. At Lallubhai Compound, the level stood at 226, 223, and 413 μg/m3 for the same zones.

“SRA is a fantastic policy from the economic and housing point of view,” said lead researcher Ronita Bardhan, lecturer of sustainable built environment, University of Cambridge, UK. “However, a relook at the policy is necessary since the design of these houses is not considered, and health and well-being consequences of the SRA are unknown.”

The study also found that infiltration of ambient (outdoor) air into the household significantly contributed to indoor air pollution, and SRA architects should keep this factor central to the design and construction of the exterior and ventilation systems.

Despite 75-85% of the surveyed households using LPG stoves, PM2.5 inside/outside (I/O) air quality ratio exceeding 1.0 was recorded in 45.7% of Dharavi residences and 44.7% in Natwar Parekh tenements. Only 20.5% of houses at Lallubhai Compound crossed the 1.0 I/O ratio.

Environmentalists said many flats on a floor – as opposed to four – in SRA buildings has resulted in both poor indoor air quality and lack of sunlight due to the absence of cross-ventilation since windows are smaller. “Ideally, wind profiling and shadow analysis should be undertaken at the planning stage of a building. Unfortunately, environmentalists at present are roped in only when the developer is applying for environment clearance, which is very late,” said Avick Sil, regional director, Environmental Policy and Research Institute.

“The administration should make it mandatory for developers to get environmentalists on board to work with architects,” Sil said.