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Assessment of health Impact among residents living near to a landfill Site in Sultanate of Oman

Improperly designed and maintained waste sites can produce irritant compounds and are implicated in contaminating the surrounding environment. Exposure to elevated levels of air pollutants is associated with both acute and chronic health effects.[1]
Sonob landfill, located close to a village called Sonob in Boushar wilayt, Muscat Governorate of Oman, and covering an area of around four sq. km., was operationalized 15. years ago within less than a kilometer of Sonob village. License issued by the concerned authorities allowed the disposal of household, commercial and industrial waste. Since the early 90's, residents living near to this landfill site voiced increasing concern that odors and smokes emitted from the site were causing illness. Symptoms and diseases reported included, in addition to bad odor and stress, eye infections or irritation, headache, cough, stuffy nose, dry throat, nausea, asthma and spontaneous abortions. Under the circumstances, it seemed imperative to study the effect of the landfill on the health of the residents quantitatively, mainly focusing on allergic disorders.
A cross-sectional study was conducted in five selected villages, Sonob, Falg sham, Hamam, Aqbia and Gala. All the people residing in the sampled cluster/village were included in the study. The objectives were to estimate the prevalence of allergic disorders in the area near the landfill as compared to the other selected villages, to quantify the ambient landfill associated air pollutants in the selected villages, and to study the effect of the landfill on allergic disorders and air pollutants.
Three data collection instruments were designed to collect the information for each village, household and individual, in a hierarchical pattern. The information collected included basic socio-demographic information; household environment; duration of living in the region; smoking; suspected landfill associated illnesses including respiratory diseases, stillbirths/abortions, congenital anomalies, conjunctivitis, dermatitis and cancer. The ambient air concentration for different toxic gases was measured at the landfill and the five study villages by using an apparatus called MIRAN 103. The concentration of 15 toxic gases on the landfill site and study areas were measured. A total of 1213 individuals were interviewed. There was no significant differences in household characteristics or socioeconomic status between the five villages.
Diseases which predominantly had an allergic or irritative cause, including difficulty in breathing, bronchial asthma, dry cough, bronchitis, rhinitis, dermatitis and conjunctivitis; were grouped together and labeled as Allergic Disorders. Sonob had the highest prevalence of allergic disorders (Table 1). In general, the prevalence of allergic disorders increased the closer people lived to the landfill. The association between prevalence of allergic disorders and distance from the landfill showed an odds ratio of 0.77 (95% CI 0.73-0.81).
When the association was examined after controlling for each of the sociodemographic, household and environmental factors using multiple logistic regression (Table 2), there was practically no difference between the crude and the adjusted odds ratios, indicating that none of these variables were confounders. Even controlling for all the three groups together did not produce a significant change in the OR. These results show that the association between distance from landfill and the prevalence of allergic disorders was independent of all the potential confounding factors studied.
The concentration of all the 15 gases measured showed a statistically significant inverse association with increasing distance from the landfill, and 10 were found to be above the normal permissible limits.
Data was also analyzed using the ecological technique to study the relationship between distance from landfill, concentration of ambient gases in different villages and the prevalence of allergic disorders. The grouped prevalence of allergic disorders had a good correlation with the distance from landfill (r = -0.734) but was not statistically significant. When the effect of distance from the landfill was controlled for, although the correlation coefficient remain reasonably large, the relationship became statistically not significant. This change suggests the presence of some alternate mechanism to describe the relationship between allergic disorders and landfills, which is only partially explained by the emittent gases studied.

Editorial note:

Human exposure to air pollution may result in a variety of health effects depending on the type of pollutants and the magnitude of exposure. The WHO has been concerned with air pollution and its impact on human health for over 40 years. However, the first edition of the WHO air quality guidelines was published in 1987.[1,2] The investment in investigating, monitoring, assessing and controlling pollution helps to avoid adverse outcomes to heath and ecosystems, which are usually more costly then preventive actions.
Most modern landfills are carefully designed structures built into or on top of the ground, in which trash is physically isolated from the surrounding environment. This is accomplished with a bottom liner, either a synthetic plastic liner or a clay liner, to isolate the trash from the environment, and a daily covering of soil.[3]
A number of landfill gases are generated during the natural process of bacterial decomposition of municipal solid waste. A number of factors influence the quantity of landfill gases generated and their composition. These factors include but are not limited to the type of waste in the landfill, its moisture content, acidity and temperature.[3] The generated landfill gas consists of a mixture of gases; 50% methane, 45% carbon dioxide, small amounts of hydrogen sulfide, oxygen, nitrogen oxides, and trace amounts of non-methane organic compounds.[1,4] It has been estimated that each ton of waste has the potential to generate approximately 400 cubic meters of bio-gas over a period of 10-15 years. Most modern landfill sites are tightly sealed units, which generally slow the degradation process and, as a result, a landfill can continue to produce gases even after a period of 50 to 100 years.[5]
Epidemiological literature on health effects related to residence near landfill sites have showed an increased risk of adverse health effects. Low birth weight, birth defects, certain types of cancers, respiratory diseases and psychological disturbances.
In 1998 a study explored the health of residents living near 23 landfill sites across Europe which showed that living near a landfill site was associated with a 33% increased risk of non-chromosomal anomalies, such as neural tube defects, cleft palate, and certain cardiovascular and gastrointestinal disorders.[6] Another study conducted around Montreal landfill reported modest excess risks for stomach cancer (RR 1.14, 95% CI 1.01-1.45) and cancer of the cervix (RR 1.23, 95% CI 1.04-1.45) among women, and fewer than expected breast cancers. Among men, a modest excess risk was found for stomach cancer (RR 1.24, 95% CI 1.06-1.44) and for cancer of the liver and intrahepatic ducts (RR 1.79, 95% CI 1.212.64). Modestly elevated RRs were also seen for lung cancer.[7]
Regarding landfill odors, which represent more of a public nuisance than a health hazard, for some people, simply smelling an unpleasant odor can be sufficient to create an adverse physiological response like headache, nausea, appetite loss, irritability and fatigue. Effects on well-being may certainly affect immunity and susceptibility to disease.[8]
It was recommended that the landfill site be closed or moved from the residential area if possible. Air pollutant gases should be regularly monitored at the landfill and area around it. Landfill gas should be treated either by burning in a flare or by use of absorbent material within the landfill. All landfill sites should be constructed at least 20-30 km away from residential areas, keeping in mind the direction of construction and building expansion. Further studies should be conducted, and investigating other sources of environmental pollution, such as water and soil.
  1. Elliott P, Briggs D, Morris S, et al. Risk of adverse birth outcomes in populations living near landfill sites. BMJ 2001; 323:363-368.
  2. WHO European center for Environmental and health. Concern for Europe's tomorrow. health and the environment in the European region. Stuttgart: Wissenschafiliche Verlagsgesellschaft.1995.
  3. Landfill solid waste (or sanitary) landfill for safe disposal of regular household garbage, and a hazardous waste landfill. recyclecity/landfill.htm.
  4. U. S Environmental protection Agency. region 3: Mid-Atlanta region Hazardous sit cleanup division, landfill gas. 16/9/2001
  5. Agency for Toxic Substances and Disease Registry. Health Consultation: Methane Migration at Landfills 8 and 10, Wright-Patterson Air Force Base, Dayton, Ohio. Atlanta: U.S. Department of Health and Human Services. September 12, 1990 www.; www.background landfill gas.htm. on 16/9/2001
  6. Vrijheid M. Health effects of residence near hazardous waste landfill sites: a review of epidemiological literature. Environ Health Perspect 2000; 108: 101-112
  7. Goldberg M, Al-Homsi N, et al. Incidence of Cancer among Persons Living near a Municipal solid waste landfill site in Montreal, Quebec. Env Res 1995; 50:416-424
  8. Weisse C. S. 1992. Depression and Immunocompetence: A Review of the Literature. Psychol Bulletin 3:475489.