Heavy metal pollution from road dust is a potential health risk: Warns study
The article illustrates how heavy metal pollution in a developing country like ours severely affects the health of its residents. It is based on a recently published study carried out in Kolkata by a research group in IISER Kolkata’s Department of Earth Science.
The city of joy - Kolkata, is the second-most polluted metropolis in India, as stated by the World Health Organization in 2018 (WHO, 2018). Prolonged exposure to heavy metals like magnesium, chromium, lead, nickel, copper, which are common city-pollutants, are known to pose significant threats to ecosystems and human health. Heavy metal accumulation in humans is known to cause adverse health problems leading to growth retardation, kidney disease and various forms of cancer (Shabbaj et al., 2018).
Road dust acts as a mobile source a sink for the heavy metals released into our surroundings (Men et al., 2018). We are exposed to it either through direct skin contact or inhalation through the nose and mouth while breathing. A group of researchers from IISER Kolkata collected road dust samples across 57 spots in the city, across 6 different types of land - residential, roadside, traffic, railway, port, and industrial, to check heavy metal contamination levels in the city. The road dust samples were analyzed for 11 major and trace heavy metals. Zinc, copper, lead, and chromium were found in higher amounts than the others.
Lead is released into the environment by automobiles running on lead-based petrol, burning of fossil fuels like coal, and smelting industries. Although lead-based petrol in India was banned in 2001, lead has a high persistence time and can stay for long in the environment, once released (US-EPA, 2017). Chromium adds to the pool from metallurgy or electroplating industries. High levels of lead in blood have been associated with disorders like ADHD (Attention-deficit hypertensive disorder) and high chromium levels are known to impair neurological development in children (Roy et al., 2009).
“What we found was that there was no significant difference in heavy metal contamination levels between the different land use categories. Residential areas have almost similar levels of contamination compared to industries or traffic areas. Across the country of India, the different heavy metal contamination levels depends on the kind of industries and pollution sources present in the particular state” says Dr. Sayantan Sarkar, from the Department of Earth Sciences at IISER Kolkata and principal investigator of the research group that conducted the study.
Road dust acts as a matrix, between other sources of heavy metal pollution i.e. soil and water. During heavy rains, the road dust pollutants are washed into sewage waters which can then mix with the soil- the other two sinks for heavy metal contaminants. The results of this city-wide study showed similar heavy metal contamination levels across the different land use categories. The health index for adults and children was calculated and the contaminant levels of carcinogenic heavy metals like lead, nickel, and chromium indicated a higher risk of cancer in children. When compared to other countries, the heavy metal contamination level in the city of Kolkata was found to be similar to the industrial countries of China and Bangladesh, which report higher than safe levels of lead and chromium in road dust respectively (Rahman et al., 2019; Pan et al., 2017; Men et al., 2018).
In Kolkata, the north and central-west regions were found to be the heavy metal contamination hotspots in the city, compared to the recently developed south Kolkata. The older places in the city, with constructions dating back to British times, are more congested and lack a distinction between residential and industrial spaces. In the future, keeping separate land spaces and creating separate zones for industries and residential regions would reduce the exposure to heavy metal pollution, reducing health risks. Therefore, the findings of this study should be taken into consideration by policy-makers and city development officers during the development and construction of industries in any residential city.
Location of the sampling sites. The figure on the left shows the state of West Bengal (in blue) and megacity Kolkata (yellow circle). The figure on the right shows the locations of the 57 sampling sites in Kolkata and their corresponding categorization based on land-use. Also shown are locations of thermal power plants and the international airport (Sayantan Sarkar et al). Bibliography
Gunjan Misri is a 5th-year BS-MS Student of IISER-Kolkata, majoring in Biology. Her hobbies include singing and trying hands at any instrument she sees or hears (currently into piano and ukulele). She enjoys reading occasionally and uses colors to express herself.
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