«Signature: _ April 13, 2012 Vijay Selvan Ram A Deterministic and Probabilistic Analyses of the Carbon Tetrachloride Contaminant Plume in Groundwater ...»
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April 13, 2012 Vijay Selvan Ram A Deterministic and Probabilistic Analyses of the Carbon Tetrachloride Contaminant Plume in Groundwater at the Former Union Carbide India Limited Factory in Bhopal, Madhya Pradesh, India By Vijay Selvan Ram Master of Public Health (MPH) Global Environmental Health P. Barry Ryan, Ph.D Committee Chair Ramana Dhara, MD, ScD Committee Member Morris Maslia, P.E., D.WRE, DEE Committee Member Paige Tolbert, PhD Committee Member A Deterministic and Probabilistic Analyses of the Carbon Tetrachloride Contaminant Plume in Groundwater at the Former Union Carbide India Limited Factory in Bhopal, Madhya Pradesh, India By Vijay Selvan Ram BS Georgia Institute of Technology 2006 Thesis Committee Chair: P. Barry Ryan, Ph.D An
of A thesis submitted to the Faculty of the Rollins School of Public Health of Emory University in partial fulfillment of the requirements for the degree of Master of Public Health in Global Environmental Health 2012 Abstract A Deterministic and Probabilistic Analyses of the Carbon Tetrachloride Contaminant Plume in Groundwater at the Former Union Carbide India Limited Factory in Bhopal, Madhya Pradesh, India By Vijay Selvan Ram The Union Carbide India Limited (UCIL) factory in Bhopal, Madhya Pradesh is the site of one of the world’s worst industrial disasters. In 1984, a gas release of Methyl Isocyanate (MIC) caused the deaths of thousands within weeks and thousands more since. After this incident, the factory operations ceased and the site was abandoned. However, remediation activities have yet to take place, which means that the pesticide products and their production intermediates serve as ongoing pollutants to the environment, in particular, the groundwater. In order to evaluate the effect of this contamination, the following study attempts to describe the contaminant plume of carbon tetrachloride (CCl 4 ) in the groundwater using analytical models provided by publicly the available software known as analytical contaminant transport analysis system (ACTS). CCl4 is known to have adverse effects on human health when consumed through the drinking water and is classified as possibly carcinogenic by the Department of Health and Human Services (DHHS). The calibrated deterministic results show that concentrations of CCL 4 do not exceed the U.S. EPA maximum contaminant levels (MCLs) roughly 850m from the source in the northeast direction. Probabilistic simulations show that there is a 100% probability that CCl 4 concentrations exceed WHO specified MCL up to the year 2034 at sites 500m, 1000m and 2000m northeast of the UCIL site. Analytical models are an effective tool in decision making for environmental managers and policymakers. As many of the parameters used as inputs for the analytical model were based on sparse field data and literature values, it is recommended that future studies should aim to better characterize the hydrogeological system of which the land surrounding the UCIL site is a part. This information will help to generate more representative analytical models with which to analyze the contaminant plume.
A Deterministic and Probabilistic Analyses of the Carbon Tetrachloride Contaminant Plume in Groundwater at the Former Union Carbide India Limited Factory in Bhopal, Madhya Pradesh, India
I would like to thank Dr. Ramana Dhara and Morris Maslia for their support throughout the process of writing and researching. Their willingness to take on this project is a courtesy I am extremely grateful for. I would also like to acknowledge Dr. Barry Ryan for his support and time spent discussing and working through many aspects of this thesis.
Table of ContentsI. Background (p.1 – p.3)
1. The Bhopal Syndrome
2. The Infamous MIC-tank Explosion
3. Health Effects of MIC-Exposure II. Introduction (p.3 – p.9)
1. Union Carbide India Limited
2. Contaminated Groundwater in Bhopal
3. Study Objectives
4. Chemical and Contaminant Properties of Carbon Tetrachloride III. Methods (p.9 – p.12)
1. Modeling Approach and Assumptions
2. Model Input Parameters and Source Definitions for Deterministic Simulations
3. Model Input Parameters for Probabilistic Simulations IV. Results (p.12 – p.13)
1. Calibration Results
2. Deterministic Model Simulations
3. Probabilistic Model Simulations V. Discussion and Conclusion (p.13 – p.16)
1. Contaminant Plume
2. Study Limitations VI. References (p.17 – p.19)
Figure 1: The Central Indian State of Madhya Pradesh (p. 20) Figure 2: Center for Science and Environment Schematic of UCIL Factory (p.21) Figure 3: Greenpeace Sampling Locations at the UCIL Factory in Bhopal, India (p.22) Figure 4: NEERI: Location of Suspected Dump Sites (p.23) Figure 5a-c: Deterministic Simulation Results for Calibration Target and Model Simulation (p. 24 – 26) Figure 6a-b: PDF histograms for Probabilistic Simulations (p.27) Figure 7a-c: Probabilistic Simulation Results 500m from the Source (p.28 – p.30) Figure 8a-c: Probabilistic Simulation Results 1000m from the Source (p.31 – p.33) Figure 9a-c: Probabilistic Simulation Results 2000m from the Source (p.34 – p.36)
The push to increase the productivity of agricultural lands through the application of pesticides begins in earnest after World War 2. David Weir, in his book, The Bhopal Syndrome, details the consequences of this effort. Increasing food production was possible by the application of increasing amounts of pesticides on crops. As a result, the pests being targeted began to develop resistance to these chemicals, which in turn led to an increasing amount of pesticides being sprayed on agricultural land, in a phenomenon termed the “pesticide treadmill” (Weir 1988). Pesticide manufacturers, experiencing saturated markets in the west, turned their attention to the export market with plans to develop manufacturing facilities closer to these markets in the developing world. In India, specifically, they found the absence of any stringent regulatory framework conducive to increasing what were becoming slim profit margins. These same regulatory policies would later be to blame by some for the poor conditions of pesticide plants around the country. The Union Carbide Corporation (UCC) was among the many multinational corporations producing pesticides, and the Union Carbide India Limited (UCIL) was the subsidiary branch operation in Bhopal, Madhya Pradesh (Weir 1988).
The Infamous MIC Gas Release Bhopal, the site of UCIL, is the administrative capital of the central Indian state of Madhya Pradesh (Figure 1). On the night of December 2nd 1984, one of the world’s worst industrial disasters occurred at the UCIL site (Figure 2). Due to faulty safety systems and corrosion of the methyl-isocyanate (MIC) storage tank, water was inadvertently introduced into the 40 ton tank of MIC, causing an extreme exothermic reaction with
and escaped into the environment (Labunska et al. 1999, Bucher 1987). Because MIC gas is more dense than air, and because of the relatively static wind conditions at the time, the gas cloud lingered in the ambient atmosphere where hundreds of thousands of residents residing in poorly insulated slum-dwellings and other apartment dwellings were exposed (Greenpeace 1999, Weir 1987) Health Effects of MIC-Exposure MIC, being an intermediary in the production process, was not widely studied in the field of toxicology before the gas explosion. However, this changed after the incident, when studies into the health effects of exposure to this gas became necessary (Bucher 1987). John Bucher notes that MIC has poor warning properties as it falls below the threshold of human detection, making it an especially potent toxin. In addition to the approximately 2,500 deaths, the exposure manifested itself in a number of adverse health outcomes for more than 100,000 people (Dhara et al. 1995). A number of studies have been done to date cataloging the acute- and long-term health effects. Epidemiological studies in the early aftermath of the incident describe the acute symptoms associated with exposure to MIC.
A survey conducted by Andersson et al. two weeks after the incident reported that the most common symptom among survivors was burning eyes. The authors go on to postulate that the irritating effect caused many residents to run outside of their homes in the direction of the gas cloud, thereby increasing their exposures. The survey participants were grouped into eight different housing zones exposed to the gas with two control groups. Diarrhea was reported with greater frequency in zones with greater mortality
nose and throat, vomiting, urination and psychological manifestations such as depression, confusion and panic (Bucher 1987). In follow up studies, permanent changes to lung pathology were observed (Kamat et al., 1985).
In a review of the epidemiological studies linking health effects to MIC-exposure, written by Dhara et al. in 2002, longer-term health effects have been observed. Longerterm effects from MIC exposure have included chronic inflammation of the eye and inflammation of lung cells (Dhara and Gassert 2002). The review goes on to catalogue an increase in spontaneous abortions among households severely affected. In utero exposure to MIC gas has also led to a persistent hyper-responsive cellular and humoral immune state in affected individuals nearly twenty years after the incident (Mishra et al. 2009). A recent mortality figure associated with MIC exposure is estimated to be around 5,000 (Sarangi et al. 2010).
The threat to health from MIC-related exposure is ongoing, however, there are other environmental threats associated with the UCIL site that also demand attention.
There is plenty of evidence to suggest that the UCIL plant is responsible for a number of toxic chemicals found in the groundwater supplying drinking water for residential neighborhoods in the vicinity of the plant (Labunska 1999).
Union Carbide India Limited The UCIL plant was in operation from 1977 to 1984. During that time they were
charged with producing three different kinds of pesticides and their intermediates:
Carbaryl, also known as Sevin, phosgene, monomethylamine (MMA), MIC, Aldicarb and
manufacture Sevidol, γ-HCH must be extracted from technical grade HCH, which includes an α-, β- and δ- isomer. After extraction, the remaining isomers are discarded as waste (Johnson et al. 2009). MIC, which was manufactured on site, in the presence of alpha-naphthol and carbon tetrachloride (CCl 4 ) produced Carbaryl. In addition to the aforementioned products, a number of other chemicals were used at the site for producing pesticides including chloroform as a solvent and heavy metals for sealants (Labunska et al. 1999).
Contaminated Groundwater in Bhopal Dixit et al. conducted a study on the Shahpura Lake in Bhopal and found levels of copper, chromium, lead, cadmium and manganese higher than permissible levels. The authors postulate that these heavy metals arise from wastewater sources. Because this lake is used for fishing, there is the danger that these heavy metals will end up in the human body after bioaccumulating through the food chain (Dixit et al. 2008).
The extensive use of pesticides has also led to large-scale organochlorine contamination in drinking water sources. Dikshith et al, in a study examining residues of DDT and hexachlorocyclohexane (HCH) in major sources of drinking water in Bhopal, collected sixty water samples from different wells, handpumps and ponds and subjected them to GLC analysis. The well water showed levels of HCH between 1.576 – 7.747 parts per million (ppm) and levels of DDT between 3.153 – 9.356 ppm. Again, these compounds have the potential to bioaccumulate through the food chain, posing potential risks for those exposed (Dikshit et al., 1990).
In a different study, Dikshith et al. study levels of 1-Naphthol in soil and drinking
level of 1-naphthol with a range between 0.017 – 0.048 ppm with pond samples having a higher residual content. While the authors do note that the clinical and toxicological effects of 1-naphthol exposure are poorly understood, the presence of these chemicals, used for the production of pesticides, should be a major concern (Dikshit et al. 1990).
This research highlights the concentrations of pollutants in drinking water and recreational water supplies in Bhopal; however, a number of studies document groundwater contamination as a consequence of the routine operations of the UCIL factory and the absence of management or remediation of the site following the MIC gas explosion.
Greenpeace Labunska et al., associated with Greenpeace International, carried out an extensive survey of the soil and groundwater at the UCIL site in the summer of 1999.
From a collection of soil-sludge taken in the former Sevin structure plant, elevated levels of mercury were found in a drain, which indicates contamination with a number of other heavy metals (chromium, copper, lead, nickel and zinc), all found at levels above background. From this sample they also isolated 73 organic compounds of which 49% were reliably identified. Polycyclic aromatic hydrocarbons (PAHs) among them are extremely toxic to humans. In addition to PAHs, hexachlorobutadiene and hexachloroethane were identified in this sample.