CHENNAI: As Metro Rail construction cutting across key stretches of the city is triggering sharp, localised spikes in dust and noise, nearly half of the residents in affected areas are reporting discomfort, even as overall air quality largely remains within prescribed limits, a new study has found.
The assessment spans Corridor 3, running from Madhavaram in north Chennai to SIPCOT along the IT corridor, and Corridor 4, which connects Light House to Poonamallee. The study covered a wide network of neighbourhoods, including Ayanavaram, Otteri, Pattalam, Kellys, Purasawalkam, Perambur Barracks Road, Thoraipakkam, Mettukuppam, PTC Colony, Okkiyampet, Karapakkam, Okkiyam Thoraipakkam, Okkiyam Maduvu, NH4 Bypass-Poonamallee junction, Kumananchavadi, Alwarthirunagar, Vadapalani, Kodambakkam and Santhome.
The study, conducted by researchers from multiple academic institutions, including SRM Institute of Science and Technology, has been published in the journal Scientific Reports, a peer-reviewed publication under the Nature portfolio.
Tracking pollution across pre-monsoon, monsoon and post-monsoon phases, the study establishes a clear seasonal trend: dust levels surge during the dry months when excavation and material handling peak, and ease during the monsoon due to rain. PM 2.5 levels reached up to 39 µg/m³ and PM 10 up to 80 µg/m³ during the pre-monsoon phase, both within national standards, before declining in wetter months.
Sulphur dioxide and nitrogen dioxide remained within limits across seasons. However, carbon monoxide (CO) showed marginal exceedances, touching 2.60 mg/m³ against the 2 mg/m³ standard in traffic-heavy zones influenced by construction activity.
"Higher concentrations were consistently observed near active construction sites, with vehicular movement compounding the impact," the study noted.
Noise pollution, however, has emerged as a more persistent concern. Levels frequently approached or breached permissible limits, particularly in dense commercial and mixed-use areas such as Vadapalani, Purasawalkam and Perambur. Peak disturbances were recorded during morning and evening hours, when construction activity coincided with traffic flow.
"The highest noise levels were observed when construction and traffic activity overlapped," the report said.
The environmental stress was reflected in public health responses. A survey across the corridors found that nearly half of the residents living close to the construction zones reported symptoms such as dizziness, breathing difficulties, eye irritation, headaches and sleep disturbances.
In Corridor 3A (north and central Chennai stretches), 20.2 per cent reported breathing issues and 24.4 per cent headaches, while in Corridor 3B (southern and OMR stretches), nearly 49.8 per cent reported dizziness-like discomfort.
In Corridor 4, 23.5 per cent reported headaches and 16.9 per cent breathing problems, indicating a clear spatial link between exposure and health complaints.
"Respiratory and eye irritation were more common in high-dust areas such as Ayanavaram and Purasawalkam, while sleep disturbance and perceptual discomfort were more frequent in high-noise zones like Perambur and Thoraipakkam," the researchers observed.
Despite the short-term strain, the study stresses that the impacts are temporary and manageable. It recommends targeted mitigation measures, including water spraying to control dust, installation of acoustic barriers, regulated working hours and continuous environmental monitoring.