Mumbai’s smog has an unlikely culprit: Salt from the sea

Mumbai's haze has a surprising source: sea salt. The city's air remained enveloped in a thick veil on Thursday, with the civic administration pinpointing sodium chloride, or common sea salt, as a contributing factor. This marks the first time the administration has flagged sea salt as a haze-causing agent, as air pollution has been a rising worry in the city since 2022.

The culprit lies in El Niño, a climate pattern that brings warmer temperatures and altered rainfall patterns to the Asia-Pacific region. In Mumbai, this climate phenomenon accelerates evaporation in the Arabian Sea, leading to waves that churn up sea spray and aerosols, which enter the atmosphere. As these particles evaporate, salt remains suspended in the air, creating a haze that hampers visibility.

Dr. Tuhin Banerjee, an air quality expert and former scientist at the National Environmental Engineering Research Institute (NEERI), explained that sea salt, or NaCl, is a particle that directly impacts visibility, forming a dense haze around the city's skyline. Moreover, these salt particles can combine with man-made emissions, such as nitrogen and sulphur oxides from vehicles and industries, potentially nurturing the creation of secondary pollutants.

The situation may be exacerbated by lower wind speeds, which can trap these particles in the atmosphere for extended periods. While sea salt aerosols have not been proven to pose significant direct health risks, Banerjee noted that they could react with other atmospheric compounds to create secondary pollution. Over time, these salt particles can also corrode electrical equipment, including circuit boards and mobile phones.