Thalassogenic infectious diseases caused by wastewater pollution of the marine environment: An estimate of the worldwide occurrence

Abstract

This chapter presents a preliminary order of magnitude estimate of the GBD associated with swimming/bathing in wastewater polluted coastal waters, and with eating raw or lightly steamed filter-feeding shellfish/mollusks harvested from suchwaters, polluted with pathogenic microorganism of fecal origin. These infectious diseases related mainly to pathogens carried by land-based sources of wastewater pollution of the seas have been called in this chapter Thallasogenic Disease. Until recently, these human health effects, associated with pathogenic microorganisms mainly from wastewater from land-based sources disposed of into the marine environment have been considered to be primarily of a local nature and have not been included in the world agenda of marine scientists dealing with global marine pollution problems. The massive global scale of the problem can be visualized when one considers that the human body wastes, which carry the full spectrum of microbial pathogens of a significant portion of the world population-about 50%-who reside along the coastline or in the vicinity of the sea are continuously discharged directly or indirectly into the marine coastal waters, much of it with little or no treatment. This study has estimated that globally, foreign and local tourists together spend 2 billion man-days annually at coastal recreational resorts and are often exposed there to these wastewater polluted coastal waters. It has been estimated that annually the world population consumes 800 million meals of potentially contaminated shellfish and other seafoods grown and/or harvested in wastewater polluted coastal waters. On the basis of risk assessments from theWorld Health Organization and academic research sources, it has been estimated that globally, each year, there are 120 million excess cases of gastrointestinal disease and 50 million excess cases of the more severe respiratory diseases caused by swimming in wastewater polluted waters. It has also been estimated, by this study, that there are 4 million cases of infectious hepatitis (HAV/HEV) with 40,000 deaths and 40,000 cases of long-term disability annually from consuming raw or lightly steamed shellfish/mollusks harvested from wastewater polluted coastal waters. The total estimated impact of the human disease associated with land-based marine pollution by sewage may be about 3 millionDALYs/yr, with an estimated economic loss of 12 billion dollars per year. If one compares these estimates with estimates of other known diseases of global public health importance for which DALYs have been calculated by Murray and Lopez (1996), it can be seen that the loss of life years and their associated economic loss estimated to be caused by marine pollution from land-based sewage is very significant, with the impact being similar to that of upper respiratory tract infections and intestinal nematodes worldwide (Table 16.1). It is necessary to caution here that all of the above estimates are at best only first approximations that must be taken with reservations and used with caution. The approach used is macro with many simplifying assumptions, extrapolations, and approximations. Thus, it is appropriate to assume that all of the above figures are no more than rough order of magnitude estimates and that the true figures may be 50% or so greater or less. While the methodology used may serve as an illustration of how one might go about estimating the global impact of disease associated with polluted marine coastal waters it must be refined if more accurate and dependable estimates are to be made. However, hopefully these preliminary estimates will serve as a basis for determining an order of magnitude of these problems that are undoubtedly of global scope and of the massive health and economic implications in the multi-billion dollar range every year. They suggest that they add up to an issue worthy of inclusion on the global agenda of marine pollution prevention and control.