We have talked about Diwali last week and we will look at some other pollution days in India this week.
There is a unique practice in India that during some festivals, people make idols of the gods they worship, and immerse them in waterways. For example, Durga Puja (aka Durgotsava or Sharodotsava), a huge festival in the west Bengal region involves a ritual of immersing Durga idols. In the Hindu religion, such a practice symbolizes the deity Durga’s return back to the divine realm after defeating an evil Asura that harmed human society. Hindu people show respect and gratitude to their god through such a practice. Similar practices also exist in other festivals like Ganesha Utsav.
Durga idol immersion ritual (photo credit: Rajesh_India)
Unfortunately, such a practice has caused major water pollution in Indian rivers like the Ganges river. Research done by Dibasish et al (2021) revealed a drastic increase in water quality parameters like biochemical oxygen demand (BOD), chemical oxygen demand(COD), and total dissolved solids(TDS), after Durga Puja. As a result, the water quality index of the Ganges river decreased from 0.5 to 0.3. Water pollutants are believed to come from two major sources, the material used to construct the idols and the dyes used for decoration.
WQI comparison before and after Durga Puja (photo credit: Dibasish et al)
The idols immersed vary in size, from 30 centimeters tall idols that are for personal worship, to several meters tall statues used by religious groups. The idols are traditionally made from clay and mud. Nowadays, there are many idols that are made from Plaster of Paris (POP) in order to reduce their weight and cost. POP contains phosphorous, CaSO4, sulfur, and magnesium( Sanjay et al., 2018). CaSO4 is a barely soluble salt in water and it slowly produces sulfate ions, which increase water acidity. This can be proven by the decrease in pH observed after Durga Puja (Ruhi et al, 2020). The immersion activity will also lead to eutrophication as explained by Ruhi et al (2020), the increasing BOD level suggests a high nutrient level in the water body.
Traditionally, people used natural dyes for the exquisite decorations on the idols but currently, most paints used are artificial dyes. Such dyes contain heavy metals like lead (Pb), chromium (Cr), and cadmium (Cd) (Abhijit & Sufia, 2020). In their research, they discovered a huge increase in the concentration of dissolved heavy metal ions after Durga Puja at almost all study sites.
(photo credits: Abhijit & Sufia)
Heavy metals are known to cause damage to human bodies, and their ability to bioaccumulate. Usually, the government establishes water treatment plants to ensure drinking water safety. However, in India, the risk of heavy metal intoxication may be more severe as local people have a religious tradition that encourages drinking directly from the Ganges river. Moreover, the synergistic effect among pollutants may worsen the problem. In this case, immersion of idols leads to an increase in both acidity and heavy metal concentration. Based on the study done by Tasneem et al (2009), Lethal concentrations (LC25) of chromium (VI) decrease rapidly with higher acidity. In their experiment, in a duration of 96 hours, LC25 of chromium (VI) to freshwater channel fish Nuria denricus decreases from 6.1 mg/L at pH level 7, to 4.2 mg/L at pH level 5. Under the assumption that chromium (VI) has similar toxicological effects on humans and the experiment species, drinking directly from water polluted by immersing idols poses devastating health threats to Indian people, as well as the interconnected riparian ecosystems.
Thank you for reading! See you in next week’s post!
References:
Mitra, A., Zaman, S. (2020). Water Pollution and Its Mitigation. In: Environmental Science – A Ground Zero Observation on the Indian Subcontinent. Springer, Cham. https://doi-org.libproxy1.nus.edu.sg/10.1007/978-3-030-49131-4_8
Majumder, D., Dam, M., Bhattacharjee, R., Santra, S.S., Saha, S., Saha, R. (2022). Fuzzy Model for Evaluating Water Quality of Ganga During Durga Puja. In: Mandal, J.K., Hinchey, M., Sen, S., Biswas, P. (eds) Applications of Networks, Sensors and Autonomous Systems Analytics. Studies in Autonomic, Data-driven and Industrial Computing. Springer, Singapore. https://doi-org.libproxy1.nus.edu.sg/10.1007/978-981-16-7305-4_26
Ruhi G, Rupak J, Sumit K,& Susmita B. (2020). Water Pollution due to Idol Immersion in Water Bodies of
Kolkata. International Research Journal of Engineering and Technology (IRJET) Volume: 07 Issue: 03. e-ISSN: 2395-0056. https://www.academia.edu/download/64549100/IRJET-V7I31093.pdf
Sanjay Dwivedi, Seema Mishra, Rudra Deo Tripathi, Ganga water pollution: A potential health threat to inhabitants of Ganga basin, Environment International, Volume 117, 2018, Pages 327-338, ISSN 0160-4120,
https://doi.org/10.1016/j.envint.2018.05.015.
Tasneem Abbasi, T. Kannadasan & S.A. Abbasi (2009) A study of the impact of acid rain on chromium toxicity, International Journal of Environmental Studies, 66:6, 765-771, DOI: 10.1080/00207230903465296