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Edmund E. Nkwocha
Keywords: Dumpsite, hospitalization, malaria, waste.
Goren and Hellman (2001) argue that exposure to even low levels of pollution resulting from waste accumulation can aggravate health problems especially among the most vulnerable groups. Other authorities posit that waste dumps could provide conditions in which disease vectors could persist and reproduce, although this depends on waste constituents, environmental conditions, age of the dumps and operating practices (Swan, et al, 2002; Faber and Krieg, 2001). Among these vectors are mosquitoes that cause malaria. This disease is caused by the bite of an infected female Anopheles mosquito which transmits the Plasmodium falciparum parasite into the human bloodstream; from there it travels to the liver, where it grows and multiplies from a
period of 8 days to several months and even years (Afolabi, 2006).
This study examined the health effect of a waste dumpsite on the population living in proximity to it. It tries to establish whether there is a strong link between pathological zones created by the dumpsite and the incidence of malaria; whether the proximity of a residential area to municipal waste dumpsite has a significant influence on the rate of hospitalization of children due to malaria disease.
Materials and Methods
Market site, all running parallel to a major transportation route (Douglas Road), and in the North by Royce Road. Its location is therefore distinct and interesting for such a study. Secondly, although some commercial activities are practiced along the streets and major roads bordering the area, the zone is mainly residential, with a very high population density. The final reason is the willingness of residents to cooperate with anything that has to do with the dumpsite, because of its high nuisance value within the neighborhood.
However, as a result of lack of waste collection systems in the area, most residents found it most convenient to dump their waste on an undeveloped piece of land located few meters away from the nearby Otamiri stream, which in fact, serves as a source of water supply to many communities downstream (Nekede, Ihiagwa, Obinze). Refuse has been dumped on this site for more than 15 years, on a surface area approximately 6 hectares in size, 5 meters high and uncovered. Nearly 10 tons of wastes are dumped here each day. Waste components mainly include metals, (beverage cans, ferrous materials), used papers, rags, plastics and organic materials (food remnants, decaying leaves, fruits and vegetables, etc.). All these materials provided conducive environment for the anopheles mosquitoes to breed in large numbers. The area surrounding the dumpsite is highly urbanized and mainly used for mixed residential houses made up of bungalows and high-rises not exceeding two floors. The closest buildings are located at a distance of 105 meters from the dumpsite, which shows the integration of the latter within the neighborhood.
The total population of the neighborhood is estimated at about 18,563 based on the National Population Census data of 2006. From this population which fell within a Census Enumeration Zone (CEZ), a sample of 134 families having 188 children between the ages of 1 and 5 years were randomly selected using their House Enumeration Numbers. This age range of children was chosen as they
constituted the most vulnerable groups especially to malaria disease. The choice of families was validated through field visits which helped to remove over-aged children from our sample. A total of 160 subjects were finally selected for the study (n=160).
It is not easy to embark on epidemiological investigation on waste-health relationships within a population in an environment fraught with paucity of data. Data used for the study were therefore obtained through surrogate methods. A well-structured questionnaire containing basic socio-economic characteristics of the children and their parents (age and sex of children, education and income status of parents, etc) was carefully prepared. Other important variables on the housing conditions of the subjects such as presence of waste bins around homes, use of mosquito nets and insecticides were all included in the questionnaire. Parents of the subjects were also asked to indicate the number of times and month of the year their children fell sick and were admitted into the hospitals, diseases they suffered from, names of hospitals visited, and their hospital card numbers. Cases were retrospectively verified in the various hospitals where the children were treated using their card numbers. Data on these variables were requested for the past 15 months preceding our visit. For easy identification and compilation by the parents, all the requested variables were enlisted in a simple matrix format. These covariates were chosen based on previous literature identifying potential risk factors for disease exposure (Tonne et al, 2007; Khitoliya, 2004; Katsouyanni et al, 2001).
The study considered one measure of exposure to malaria infection, namely; the distance between subjects from the dumpsite. Thus, in the study area, two cordon zones were carefully delineated. The first Zone designated as Zone A, has the range of a distance between 100 and 500 meters from the dumpsite. While 110 of our subjects live in this zone, the remaining 50 subjects reside in the second zone known as Zone B, which was also in the
same neighborhood but beyond 500 meters from the dumpsite. These two zones are separated from each other by Royce and Nekede Roads. Zone B may therefore be likened to as the “clean or control” zone.
Given the limited sample size, three age groupings of the children were made (<1 year, 2-3 years and 4-5 years). To neutralize the effect of variables such as housing conditions, income and education levels of parents, etc, a logistic model was used. The exposure measures among subjects and total sample population were done using logistic regression. Risk estimates were measured in the form of Odd-Ratios (ORs). The exposure measures for malaria and rate of hospitalization among subjects were equally carried out. Analyses on the special effects of residential distance from the dumpsite and the rate of hospitalization were also made using logistic regression model in which distance was sub-divided into 100, 200, 300, 400 and 500 meters and above and included as categorical variables. Because of the sample size, the ORs were adjusted for potential confounders. Regression ANOVA and chi-square tests were used to compare major differences between the two zones. Coefficients were calculated using the Spearman rank order correlation test. Data was analyzed by SPSS for Window 10.0 (SPSS, Chicago, IL. USA)
Results and Discussion
five years, indicating that the majority of the subjects have been exposed since birth. The average educational level of parents was the West African School Certificate, with an average monthly income level hovering between N15,000 and N20,000 indicating that most of the children are of poor parentage. The average household consists of 7 persons residing in a concrete dwelling of three rooms
properly ventilated with sufficient doors and windows. Only 9 families of the subjects (5%) used mosquito nets while the greater majority made up of 151 families or 95% of the total sample did not. Also, while132 families of the subjects (83%) did not apply insecticides within their homes only 28 families (17%) used it regularly to kill mosquitoes. All the families surveyed kept their waste bins outside their homes as shown in Table 1.
Table 1: Descriptive characteristics of the study population and exposure
Age of children (years) No%
< 2 54 (33.75)
Income of parents (N) No%
Education status of mother No/%
Higher Education 15 (9.36)
Average Education 18 (11.26)
Lower Education 127 (73.38)
Housing Conditions No%
Well ventilated 151 (94.38)
Poorly ventilated 9 (5.62)
Presence of bins No%
Use of mosquito nets No%
Use of insecticides No%
Yes 28 (17.5)
Data used for the study spanned for a period of 11 months as most parents could no longer remember what happened beyond this period when filling the questionnaire. However, information obtained revealed the prevalence of malaria among subjects in the two zones investigated. A trend of greater frequency was noted in Zone A in comparison with Zone B as shown in Table 2.
Table 2: Number of subjects treated for malaria in zones A and B (n =160)
Source: Field Survey 2006/2007
Among the total sample of n=160, there were 452 reported cases of malaria among the subjects within the 11-month study period. Of this total, 399 children (88.3%) were treated in
Zone A (d < 500 meters) and 53 children (11.8%) in Zone B (d>500 meters) as shown in Table 2. Medical notes revealed that the infected subjects showed symptoms of the disease (high fever, body weakness, loss of appetite, etc). Results of their blood analyses also indicated that each of the infected children had malaria parasite, though with different degrees of infection. Also, each child that suffered from the disease spent a minimum of one day in the hospital. While the highest incidence of malaria was recorded in the month of October 2006 with 63 cases (13.9%), the least incidence occurred in February 2007 with 26 cases (5.7%). About 100 serious cases of malaria were reported with a total hospitalization period of 1174 days showing an average of 2.7 days per subject as indicated in Table 3. Also, 27% of subjects in Zone A suffered double episodes, with the duration of
the illness ranging between 3 to 5 days. Only 2% of subjects in Zone B suffered double episodes of the disease. Unfortunately, there were 19 (4.2%) reported cases of death resulting from malaria which occurred among children between the ages of 2 and 3 years old, all occurring in Zone A .
The rate of malaria incidence decreased with age and was significantly higher among subjects living around the dumpsite. The rate of hospitalization was highest among children between the ages of 2 and 3 years indicating that this group was the most vulnerable. Also, the rate ratio (RR) was significantly high (6%) among subjects in Zone A than those in Zone B (0.76%). However, this ratio decreased with age in both zones. There was no significant difference in the rate of hospitalization between the two sexes in the overall sample.
Table 3: Cases of Malaria Resulting from Proximity of New Market Residential
Source: Field Survey 2006/2007
The rate of hospitalization correlated positively with distance from dumpsite (0.83). The Spearman correlation coefficient calculated between rate of hospitalization and distance from dumpsite in Zone A was -1.12 (p<0.05) and was adjusted for other factors that may have contributed to the disease. This negative correlation indicated that proximity to the
dumpsite exposed children to the hazards of malaria infection. Similarly, the correlation coefficient of 0.14 (p<0.05) in Zone B indicates that long distance from dumpsite lowers exposure to the disease. This also implies that the rate of hospitalization decreased with increasing distance from the dumpsite with a strong evidence of a spatial trend (p<0.0001). Correlations during seasonal exposures (dry and wet seasons) were 0.77 and 0.52 and positive. Results also showed a strong association between distance from the dumpsite and malaria disease in the overall sample (OR=3.2, 95%, Cl.7-7.2). The association varied among the age groupings of the children and relative distance from the dumpsite. It was strongest for the children below 3 years of age (adjusted OR=3.3, 95%, CI 1.19-8.1) than those above 4 years in Zone A (OR=2.5, 95%, CI 1.3-6.7) and those in Zone B (OR=2.7, 95%, CI 1.38-5.7). Furthermore, the effect estimate for cumulative malaria infection increased the odds of the disease for children below 3 years of age by 9.3% per inter quartile range (IQR). The overall result showed that children living within a distance of between 100 and 200 meters from the dumpsite (Zone A) are 3.5 times more likely to suffer from malaria than those living beyond 500 meters distance (Zone B). A trend of lower incidence of malaria was therefore noted among children living in Zone B, which was the less exposed zone.
The results obtained from this study suggest that children are vulnerable to environmental diseases such as malaria. They also indicate that the level of vulnerability is a function of the level of exposure and distance to the source of the disease (Anderson and May, 1982; Fasan, 1969). It was observed that the peak period of malaria infection corresponded with months of climatic transition with low rainfalls, which encouraged the breeding of anopheles mosquitoes at the dumpsite (Okogun, 2003). This corroborates Tibbetts (2007) stance that mosquitoes and the disease they carry are especially sensitive to temperature changes. In the same vane,
Tibbetts and Epstein (2005) also maintained that warm temperatures accelerate the maturation of disease-vectors such as mosquitoes as they tend to concentrate in the same places which enhance the transmission of the paraste they carry. It is known that if the plasmodium parasite is not properly killed in the human bloodstream, it might lead to the emergence of a strain that might be resistant to drugs and frequent hospitalization of the patient (William,1996; Mendis and Cater, 1995). If the drop in the rate of infection and hospitalization in June 2006 corresponded with months of high rainfall when these vectors lay their eggs in humified waste dumps, the low value of infection recorded in the month of February 2007 may be attributed to the chilling effect caused by the Harmattan wind, when all the children are properly covered against cold, which consequently protected them from frequent mosquito bites.
Other cogent reasons emerged to buttress our argument that proximity to the waste dump increased the incidence of malaria and high rate of hospitalization among children living in the study area and these include:
Overall, our results show that the growing health disparities that result from poverty and inadequate infrastructure and service provision in our urban areas raise serious concerns about environmental justice (Thomas et al, 2006; Pellow and Brulle, 2005). The high rate of hospitalization due to malaria especially
among the most vulnerable groups such as children, and other likely diseases arising from poor management of municipal solid waste should make this sector an obvious priority. Our results constitute an eloquent testimony that children living in low income and poor neighborhoods are often at greater risk of exposure to environment-based hazards than other groups (Tillett, 2007; Been, 1993).
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