Rapp. Comm. int. Mer Médit., 36,2001
221
Any comparison of health impacts from various sources must start
with a sense of scale of the health problems. Which health impact is
more important in human disease and social terms or in financial
terms, and by how much? In this preliminary study, each of three neg-
ative health impacts has been evaluated in terms of the concept of
Global Burden of Disease (GBD). The GBD is measured in units of
Disability-Adjusted Life Years (DALYs), a new concept recently
developed by the World Health Organization (3) and the World Bank
(4, 5). This new approach calculates a) losses from premature death,
which is defined as the difference between the actual age of death and
life expectancy at that age in a low-mortality population, and b) years
of loss of healthy life resulting from disability. It is difficult to estimate
the social and economic loss of one year of productive life resulting
from premature death or disability (or one "DALY"). There are numer-
ous approaches for making such economic estimates. For the purpos-
es of this study I have estimated , in consultation with the WHO, the
money value of the economic loss of one productive year of life, or
one DALY, as being about $4,000. This figure approximates the glob-
al mean annual GDP per capita, but it is not necessarily based on that
figure (6). (See Box on how DALY’S are calculated)
Thalassogenic Diseases Related to Bathing/Swimming in Marine
CoastalWaters Contaminated by Wastewater Discharge
For the purposes of this paper we shall refer to all human diseases
associated with sources of pollution –pathogenic microorganism and
marine biotoxins, which are transported by marine waters or develop
within marine organisms as ‘Thallasogenic diseases” which in Latin
means disease caused by the sea.
There is massive epidemiological evidence that enteric and respira-
tory diseases can be caused by bathing/swimming at marine coastal
beaches contaminated with pathogenic micro-organisms, i.e., expo-
sure to pollution from domestic wastewater sources (7,8,9). The evi-
dence from 22 highly credible epidemiological studies clearly sup-
ports the conclusion that the rate of infections and disease among
bathers increases steadily with increasing concentrations of indicator
micro-organisms of fecal pollution in a dose-response relationship (9).
These studies also support the conclusion that bathers face the risk of
enteric and respiratory infection and disease even in lightly polluted
coastal waters meeting current microbial standards of the
EEC/European Union (10) and USEPA (11). Based on an extensive
and careful evaluation of the available credible epidemiological evi-
dence, WHO (7) estimated that bathing in what had previously been
considered “acceptable” marine waters with a mean concentration of
50 faecal streptococci/100 ml will result in infection and illness in 5%
of the healthy adult bathers after a single marine bathing exposure. In
this study I have estimated a 50% higher risk-of-disease rates for: chil-
dren who are known to be much more susceptible than adults; for
adults visiting beach resorts in countries with high endemic disease
rates in the local population; and for a certain percentage of highly
contaminated beaches with microbial levels higher than is considered
acceptable from a public health point of view.
Based on official reports from the WorldTourism Organisation (12)
and estimates from other sources, I have estimated that there are some
1-2 billion marine-exposure-days spent at beach resorts each year by
local residents and foreign tourists. From these global figures, and
based on the WHO risk estimates for gastroenteritis and respiratory
infections at various levels of beach pollution, a highly tentative esti-
mate has been made that some 250 million clinical cases of mild gas-
troenteritis and upper respiratory disease is caused every year by
bathing in contaminated seawater. Calculated in terms of DALYs this
results in some 400 thousand DALY units. The economic impact or
financial loss resulting from this amount of disease has been estimat-
ed at some $1.6 billion/year.
Why has this situation gone unnoticed and unreported for so long?
Epidemiological studies have revealed that minor cases of gastroen-
teritis are rarely seen by medical care professionals and even less fre-
quently reported to health authorities. The ratio of actual clinical cases
to reported cases of mild gastroenteritis can be 1000:1.
Thalassogenic Diseases Related to the Consumption of Seafood
Harvested in Marine Coastal Waters Contaminated by Wastewater
Discharge
Seafood, particularly molluscs normally eaten uncooked, is a com-
monly implicated vehicle for the transmission of infectious diseases
caused by enteric micro-organisms (including bacteria and viruses)
that enter the marine environment through the disposal of
urban/domestic wastewater. Pathogenic bacteria can remain viable in
the sea for days to weeks, and viruses can survive in the marine envi-
ronment or in the tissues of fish and seafood for months (13).
Filter-feeding shellfish, whose breeding areas are often placed near
sources of nutrients, such as wastewater outfall sewers or polluted
“THALASSOGENIC DISEASE” - HUMAN DISEASE CAUSED BY WASTEWATER POLLUTION OF THE
MARINE ENVIRONMENT WITH SPECIAL REFERENCE TOTHE MEDITERRANEAN
Hillel Shuval,
Division of Environmental Science - Herrmann School of Applied Science, Hebrew University of Jerusalem, Israel–
hshuval@vms.huji.ac.il
Society generally views recreation at the seashore and ocean bathing, called by some thalassotherapy, as a positive health experience.
However, there has been some degree of historical awareness of the potential human health problems associated with bathing and
harvesting shellfish, which are often eaten raw, in marine coastal waters contaminated by urban wastewater discharges. In the past such
forms of thalassogenic disease have been perceived primarily as isolated local problems. The issue of marine biotoxin poisonings
associated primarily with toxic algae blooms has also been of concern. However, the global disease impact and the associated economic
implications of these human health problems is estimated for the first time in this study aimed at developing a preliminary quantitative
estimate of the impact of these pathways of disease transmission (1). These findings have been underscored by other recent studies (2).
How are Disability-Adjusted Life Years- DALY’s calcula-
ted?
As an example we shall present the sample calculation of
DALY’s for a hypothetical marine pollution associated Disease
X that has caused 1,000,000 clinical cases of disease per
year globally with 10 days of incapacitation per case, 5% or
50,000 cases of life long severe disability (say partial paraly-
sis) and 1% or 10,000 cases of death. If we assume the ave-
rage age of onset of the cases of disability and death is 20
then it assumed by a special actuarial and discounting method
that the years of lost healthy life when discounted is 40. Afac-
tor of disability weight must be estimated for each disease for
the degree of incapacitation during the acute stage of illness
and the degree of disability in the case of longer term sequel-
lae resulting from the disease. The factor of disability weight
varies from 1 for total disability or death to 0.05 for very mild
cases of disease. In the case of Disease X we shall assume
a factor or 0.3 (or 30%) for the 10 days of incapacitation
during the acute stage of the disease and a factor of 0.5 ( or
50%) as the degree of incapacitation for the cases of lifelong
partial paralysis
Thus the calculation of DALY’s for Disease X would be as
follows:
a) Acute cases: 1,000,000 cases x10 day/365 days
per year
x 0.3 (factor of disability weight)
=8219
DALY’s
b) Life long disability: 50,000 cases of life long disa-
bility
x 40 years of lost healthy life x 0.5 (factor of
disability weight) =
1,000,000 DALY’s
c) Deaths: 10,000 cases of death x 40 years of lost
healthy life x 1(factor of disability weight) =
400.000 DALY’s
Total for Disease X =
1.408,219 DALY’s
say
1.4 million DALY’s
