How Bhopal reminds us of the dangers of using pesticides

Brief Introduction
On the 3rd December, 1984, the Union Carbide plant in Bhopal experienced a failure in the containment of its highly toxic chemical, Methyl Isocyanate (MIC). The cause of the pollution of 40 tons of gaseous MIC into the atmosphere was attributed to a combination of poor safety measures, safety measures that were inadequately maintained due to cost-cutting measures, poor safety training and severe overworking of staff (Ipe 2005). A combination of these issues resulted in an exothermic runaway reaction that led to MIC being released into the environment (This documentary by Seconds from Disaster shows the chain of events that led to the disaster).

Effects on humans
Post-contamination, it was estimated that “almost 20,000 people died, and nearly 200,000 people were exposed to the poisonous gas by varying degrees” (Varma and Varma 2005). The severity of the accident illustrates the dangers and toxicity of MIC.

Effects on the environment
Post contamination, as the MIC deposits, over time, the chemical makes its way into aquatic environments. Samples of the fish population in the Lower Lakes of Bhopal found that post-exposure to MIC, combined with highly eutrophic conditions, resulted in a lake that “can be considered as dead for all practical purposes” (Gupta, Sarkar and Kureishy 1991). Additionally, as MIC decomposes, it breaks down into monomethylamine, and over time, it settles towards the bottom of the lake due to “an increase of concentration with depth”, and it is unclear what are the effects of this chemical on aquatic life or humans who consume such contaminated foods (Gupta, Sarkar and Kureishy 1991).

Beyond the aquatic environment, MIC’s highly toxic properties, not surprisingly, is also detrimental to the terrestrial environment. Soil biodiversity dropped sharply post-accident, with fungal and bacteria populations, of which Actinomycetes (a type of gram-positive bacteria) populations measured in soil were significantly reduced (Parthipan and Mahadevan 1995). Actinomycetes are important for the soil due to their role in nitrogen fixation (providing usable nitrogen for plant use) and their ability to protect plants from pathogens, rendering them highly beneficial for the agricultural industry (Bhatti, Haq and Bhat 2017). The decline in soil biodiversity post-exposure to MIC was fortunately not too severe, as Actinomycetes populations returned back to normal after 30 days post-exposure (Parthipan and Mahadevan 1995).

However, this occurrence of MIC exposure by Bhopal was essentially a one-time event. MIC is a basic ingredient used to produce pesticides such as Sevin, often used by the agricultural industries globally, commonly used to kill pests such as mealy bugs and aphids, which harm plants. However, the usage of such pesticides also harms the soil these plants rely on for nitrogen as these microbes are killed by the toxicity of MIC-based pesticides, harming plant crop productivity (Shahid, et al. 2021). Additionally, while pesticides like Sevin do not persist long in the soil, its biodegraded intermediate form, 1-naphthol, is even more hazardous than the original Sevin form for organisms in the soil (Shu and Bollag 1971).

Perhaps, we should rethink how we grow our crops. The accident at Bhopal has demonstrated one of the severe effects of such chemicals, and yet, we use these to grow the food that we eat. Additionally, with soil that is essentially becoming unhealthy with more of such pesticide usage, we risk reducing the amount of food we can grow at a time when the global human population is rising, and food prices and insecurity are also rising. Could a nature-based solution be the answer?

Bibliography
Bhatti, Asma Absar, Shamsul Haq, and Rouf Ahmad Bhat. 2017. “Actinomycetes benefaction role in soil and plant health.” Microbial Pathogenesis 458 – 467. doi:https://doi-org.libproxy1.nus.edu.sg/10.1016/j.micpath.2017.09.036.

Gupta, R. Sen, A. Sarkar, and T. W. Kureishy. 1991. “Biodrgradation and Anticholinesterase activity of Methyl Isocyanate in the aquatic environment of Bhopal.” Water Research (Elsevier) 25 (2): 179 – 183. doi:https://doi.org/10.1016/0043-1354(91)90027-N.

Ipe, Mary. 2005. “Bhopal Gas Tragedy: Lessons for corporate social responsibility.” Social Responsibility Journal (Emerald Backfiles) 1 (3/4): 122 – 141. doi:https://doi.org/10.1108/eb045803.

Parthipan, B., and A. Mahadevan. 1995. “Effects of Methylisocyanate on soil microflora and the biochemical activity of soils.” Environmental Pollution (Elsevier) 87: 283 – 287. doi:https://doi-org.libproxy1.nus.edu.sg/10.1016/0269-7491(94)P4159-L.

Shahid, Mohammad, Salim Manoharadas, Hillol Chakdar, Abdulwahed F. Alrefaei, Mohammed F. Albeshr, and Mikhlid H. Almutairi. 2021. “Biological toxicity assessment of carbamate pesticides using bacterial and plant bioassays: An in-vitro approach.” Chemosphere (Elsevier) 278: 1 – 14. doi:https://doi-org.libproxy1.nus.edu.sg/10.1016/j.chemosphere.2021.130372.

Shu, Yen Liu, and Jean Marc Bollag. 1971. “Degradation of sevin by soil microorganisms.” Soil Biology and Biochemistry (Pergamon Press) 3 (4): 337 – 345. doi:https://doi-org.libproxy1.nus.edu.sg/10.1016/0038-0717(71)90044-7.

Varma, Roli, and Daya R. Varma. 2005. “The Bhopal Disaster of 1984.” Bulletin of Science, Technology & Science (Sage Journals) 25 (1): 37 – 45. doi:https://doi-org.libproxy1.nus.edu.sg/10.1177/0270467604273822.