A GIS-based modeling of environmental health risks in populated areas of Port-au-prince, Haiti

1. INTRODUCTION

Throughout the world, natural disasters have occurred over the last decades with increasing frequency and have resulted in significant mortality, morbidity, and disability among people affected, causing the destruction of physical assets and damaging social resources (UNDP 2004). They also increase the vulnerability of people, communities, and areas impacted by weakening or disabling local infrastructure, livelihoods, businesses, and regional economy (UNDP 2004). If on a global scale global warming, climatic change, and decadal variations are considered as external (but distant consequences of anthropogenic influences) triggers of the escalating of number and intensity of natural disasters, at local scale other human-induced factors such as population growth, unplanned urbanization, alteration of the natural environment, under-standard dwellings, augmentation of impervious areas, and land cultivation increases people exposure to hazards (Sorensen et al. 2006, Smucker et al. 2007). An increasingly larger proportion of the world's population is being exposed to locations at high risk (Huppert and Sparks 2006). This phenomenon is mostly observed in mega cities. Indeed, the world's population is being progressively concentrated in urban areas rather than in rural areas. It is predicted that in 2007, for the first time, more people will live in urban centers than in the countryside (Huppert and Sparks 2006).

Throughout the last three decades, the intensification of migration to urban centers, particularly in Port-au-Prince, Haiti, has resulted in the proliferation of anarchic and precarious habitats, the degradation of the resources of the environment, the deficiency of urban services, and the rupture of ecological equilibrium (IHSI 2003). Water supply and basic sanitation services are still very deficient. The 1998 edition «Health in the Americas» report of PAHO/WHO (1998) describes the situation in Port-au-Prince as follows:

«Solid waste management is a serious problem; bad excreta disposal practices are polluting almost all 18 water sources supplying Port-au-Prince. Drainage systems are inadequate and any major storm produces serious flooding. The growing number of motor vehicles and their inadequate maintenance have created a serious air pollution problem in Port-au-Prince.»

Some illustrations of the effect of environmental degradation on health are the high infestation of dengue in urban areas and the outbreak reported in 1994 in Port-au-Prince (PAHO 2001); acute respiratory infections (ARIs) accounted for 25% of deaths among children under 5 years of age, and suffered by 20% of children of this age group (EMMUS II 1994); and cardiovascular diseases that caused of the admission of 40% of patients at the State University Hospital in 1996 (PAHO 2001).

The United Nations Development Program (UNDP) (1994) considers an event a disaster when the number of human deaths is greater than 10. However, casualties resulting from environmental health hazards can be easily overlooked or even disregarded because, unlike floods or landslides that are spatially and temporally punctual, and with evident physical materialization, environmental health effects are discreet and continuous over space and time. Often the effects are not actually associated with their causes yet the casualties are countless and exceed victims of natural disasters.

On one hand it is recognized that a healthier physical environment is among the factors associated with a decline in morbidity and mortality in the past century (Corvalan et al. 1999). On the other hand high population density is considered one of the vectors responsible for health degradation and aggravation in poor countries (Campbell-Lendrum and Corvalan 2007). According to some estimates, one third of the global urban population and over 70% of people in urban developing countries live in slum-like conditions characterized by poor housing and meager basic services, with ineffective regulation of pollution (Campbell-Lendrum and Corvalan 2007). However, the impact of population densification on living conditions and health is not sufficiently well perceived, at least at the community spatial level. While qualitative information depicts the severe conditions in which the population is living, it is difficult, if not impossible, to find detailed quantitative data about the spatial incidence of a specific health hazard in Port-au-Prince. The spatial study unit used in surveys on living conditions is very coarse and doesn't allow acknowledging the reality at finer spatial scale. In Port-au-Prince, in addition to the intense degradation of the environment aforementioned, the average density found from the SDE^1(*) is more than 61,300 inhabitants per km². In some places, the density caps to more than one million per km². There's a proliferation of diseases among the population particularly in neighborhoods exposed to degraded environmental conditions such as water stagnation, waste accumulation, poorly cleaned channels, and high density housing. This situation puts in evidence the circumstances of vulnerability to which the disadvantaged urban neighborhoods are subjected.

Though Geographic Information Science GISc is relatively a new discipline in Haiti, whose usage started in the mid-1990s, no studies had attempted to link environmental health risk to causal factors using spatial analysis techniques either for Port-au-Prince or the entire country. Most studies have used traditional statistical approaches to address health issues. While the emphasis is being put on the establishment of projects and activities which aim to contribute to the realization of the Millennium Development Goals (Erenberg and Ault 2005), suitable GIS environmental models may represent an important component of such programs by attempting to link key determinants of environmental health risk to their spatial context. The ultimate output results in the localization of places where urgent interventions are to be initiated. The present study embraces this goal, and its framework comprises an assessment of the spatial susceptibility and the related vulnerability to environmental health hazards of populated places in Port-au-Prince using a geographic perspective.

* ¹ SDE = Section d'énumeration, equivalent to a US census block