Acute health effects of the Tasman Spirit oil spill on residents of Karachi, Pakistan

On 27 July 2003, the Greek tanker Tasman Spirit, carrying 67000 tons of Iranian light crude oil from Iran to Pakistan, ran aground before entering the harbor channel at the Karachi port, Pakistan. About two weeks later, on the night between 13 and 14 August 2003, the ship broke apart and released its cargo into the sea. Strong winds and rough sea facilitated the spread of oil to about 10 km of residential coastline (Figure 1). After this incident, there were two more episodes of oil spill- the latest being on 29 August 2003, resulting in a total spill of more than 35000 tons of crude oil.

The affected shoreline is a highly populated residential and recreational area. Fumes of volatile organic compounds and mist containing hydrocarbons accompanied by a strong smell dispersed into the residential area. Newspapers and the electronic media provided a wide coverage of the incident and the potential health and environmental impact of the oil spill[1, 2]. Newspapers and television channels showed pictures of piles of dead fish and turtles on the oil-covered beach. Extensive media coverage raised concerns about the potential of human health effects among residents in the affected area and among government officials.

Chemical analysis of crude oil from the tanker showed that it contained a high quantity of aromatic hydrocarbons (personal communication Lutfi SA). Crude oil is mixture of many chemicals, the major components being hydrocarbons. Iranian Light Crude oil carried in Tasman Spirit contains high quantity of sulfur (1.35% by wt), 14% light naphtha, 20% heavy naphtha and 4% gasoline and its pour point is -29°C [3]. Aromatic hydrocarbons are probably the main airborne exposure.

Spread of oil and evaporation of volatile contents after spill depends on the physical and chemical properties of the crude oil and the prevailing weather conditions. Low viscosity crude oil spreads rapidly. Low boiling point contents of crude oil evaporate within hours of the spill and if volatile contents are high then evaporation is more. High temperature, high speed wind and strong wave action increase the spread and evaporation of the volatile contents [4]. During August 10^th to August 30^th, 2003 the average maximum temperature in Karachi was 31°C while average minimum temperature was 27°C with the average mean of 29°C [5]. July and August is a rough sea season in Pakistan with strong waves. Moderately high temperature, strong waves and high speed wind [2] moved oil from sea to shoreline and winds carried vapors from sea to land. Initial assessment suggested that about 11,000 tones of volatile organic compounds entered the air after the spill. Assessment of the air revealed that on August 20, VOCs in the polluted air ranged from 44 ppm at Shireen Jinnah Colony to 179 ppm at Village Restaurant.

Residents living in this area were exposed to the high level of volatile organic compounds for at least 15 to 20 days. The level of pollutants gradually tapered off from 8 to 10 ppm of volatile organic compounds on August 30. The pungent smell was perceptible till September 5 at the distance of about 1 km from the sea [6]. These levels suggest high exposure of population to crude oil contents during spill days.

Previous investigations of the Sea Empress, the Nakhodka and the Shetland oil tankers' spills found an increased occurrence of upper respiratory tract irritation, exacerbation of asthma, vertigo, headache, and back and leg pains and psychological ailments among persons living in exposed areas and clean-up workers [7–9].

Studies on acute health effects of exposure to an oil spill are few. This paper is first of such report from a developing country. To address the concerns regarding potential health effects, we undertook an epidemiologic investigation to determine if exposure to the oil spill had resulted in increased acute ill health among the exposed resident population.

Ninety-six percent of the exposed group (207/216), 70% (58/83) of control group A and 85% (86/101) of control group B reported one or more symptoms (P < 0.001). Mean symptoms score based on the presence of 48 symptoms in a particular subject were higher among the exposed group (14.1) compared to control A (4.4) or control B (3.8). Further, mean score for each sub-group of symptoms were higher among exposed as compared to control groups. Mean score from nine ocular symptoms among exposed group were 3.4 as compared to1.1 and 0.7 for control groups A and B respectively. Mean score from seven upper respiratory tract symptoms among exposed were 3.1 as compared to 1.1 among each of control group A and B. Mean score from the five skin related symptoms were 1.0 for exposed and 0.1 and 0.1 for each of control group A and B. Mean score from 17 nervous system related symptoms was 4.3 for exposed as compared to 1.2 and 1.3 for control group A and B respectively.

We compared the proportion of each self-reported symptom among the exposed and the control groups, and found that they were highest for the exposed group located closest to the spill, followed by control group A and then B. Proportion of those who reported ever having wheezing was not different among the exposed 8.3% (18/204), the control group A 10.3% (9/84) and the control group B 5% (5/101; P = 0.329). Further, exposed 13/204 (6.0 %) who ever had episodes of wheezing that made them short of breath before the spill was not significantly different from control group A 7.2% (6/84) and control group B 3.0% (3/101, P = 0.400). After the spill, 6% (13/204) had wheezing with shortness of breath among the exposed while only 1.2% (1/82) among the control A and no one in control B.

Only 32.9 % (68/207) of symptomatic subjects in the exposed group and 29.6% (16/54) of control group A, and 19.0% (16/84) of subjects in control group B consulted a health care provider for the symptoms. Sixty-six percent (45/68) of those who consulted a health care provider in the exposed group reported only one visit. Majority (67%) of the symptomatic subjects in the exposed group reported that they had recovered completely or were recovering, whereas the remaining 33% reported that their illness was persistent.

To assess those who were more affected among the exposed, we constructed logistic regression models for each symptom as dependent variable and included age, sex, building of residence, floor of apartment, house on the main road, and presence of windows towards sea as independent variables. We found that for itchy eyes, scratchy throat, sore throat, nausea/vomiting, headache females were more likely to experience symptoms as compared to males.

A higher proportion of those who had symptoms among the exposed group 54.1% (112/207) reported interference of symptoms with their daily routines as compared to 26.8% (15/56) in control group A or 3.5% (3/86) in control group B. The average number of days that the symptomatic subjects were not able to work was significantly higher among exposed group (2.9 ± 6.3) than control A (1.0 ± 3.4) or control B (0.2 ± 1.5, P < 0.001).

This study evaluated the acute health effects of a large oil spill on a large urban population. Subjects in the exposed area had a higher occurrence in symptoms than other areas in the vicinity. There was a clear pattern of decreasing symptoms with increasing distance from the incident site. Symptoms involving eyes, throat, skin, headaches and general malaise were some of the commonly reported symptoms.

Knowledge on the health effects of hydrocarbon exposures mainly comes from studies conducted in occupational settings. Contact with petroleum or exposure to its components may result in skin irritation and stinging or redness of eyes, sore throat, breathlessness, nausea, vomiting headache, dizziness or drowsiness [10]. These are the similar symptoms as found in present study. Major hydrocarbons of toxicological interest are benzene, xylene and toulene. Moderately high concentration of these chemicals irritate mucus membranes particularly the eyes [11]. Sulfur containing components of crude oil may cause respiratory difficulty [12].

High environmental level of pollutants and increased occurrence of headache nausea vomiting, eyes symptoms, respiratory difficulties among the exposed as compared to the control groups suggests the role of pollutants in occurrence of these symptoms.

The proportion of those who developed wheezing with shortness of breath was higher among the exposed as compared to the control groups. Previous studies conducted to assess the health effects of oil spill reported an increase in occurrence of sore eyes, sore throat, headache, skin itching and rash, nausea, vomiting and breathing difficulties among those exposed to the vapors of crude oil [7–9, 13]. The results of our study are consistent with these results; exposed subjects had increased frequency of sore eyes, sore throat, headache, nausea/vomiting, as compared to the non-exposed group. Breathing difficulties also increased among the exposed group. Before oils pill the proportion of those who ever had wheezing with shortness of breath was not different among the exposed and the control groups. Further, wheezing accompanied with shortness of breath is an acute condition that occurs in bouts after exposure to certain substances which trigger it off. These substances in this particular casewere the crude oil vapors. This further suggest role of exposure in occurrence of asthmatic symptoms.

Self reported disturbance in daily routine due to symptoms further substantiate evidence about the severity of symptoms that was higher among the exposed as compared to the non-exposed groups.

We used distance to assess the degree of exposure by selecting the exposed group form the houses located on the shoreline, control group A at 2 km from the source of exposure and control group B at about 20 km from the source. The frequency of exposure as well as strength of associations for many symptoms decreased with the increase in distance. The presence of dose response also suggests a relationship between occurrence of symptoms and exposure.

Those who were exposed for a longer period of time like women among the exposed group, were more likely to develop nausea, vomiting, headache, itchy eyes, scratchy throat and sore throat as compared to men. Women spent most of their time at homes as most of them are housewives, while men were away during the day at their jobs, resulting in an increased exposure to women. These symptoms occurred after exposure to hydrocarbons [10, 11]. In other studies those who were exposed for longer period of time experienced more symptoms as compared to those who were exposed for lesser duration [7].

We analyzed data using two different approaches- multiple linear regression using symptoms score as dependent variable and logistic regression using individual symptom as dependent variable. Both of these approaches revealed strong association of exposure with the symptoms. This provides additional strength to evidence of relationship between exposure to oil spill and ill health.

This study shows a possible relationship between the oil spill and acute symptoms among residents near the spill, indicating an adverse effect on their health. Efforts should be devoted to prevent future occurrence of such incidents through instituting an emergency response and preparedness system. Long term health impact of the crude oil spill exposure should be investigated.