Transcript Drinking water and health Luiza Gharibyan Associate professor of Yerevan State Medical University Department Hygiene and Ecology.

Drinking water
and health
Luiza Gharibyan
Associate professor of Yerevan
State Medical University
Department Hygiene and Ecology
WHO Water/Health Facts
• Every 8 seconds a child dies of waterrelated disease
• 5 million per year die of illnesses linked to
– unsafe drinking water,
– unclean domestic environments, and
– improper excreta disposal.
• Nearly ¼ of humanity remains without
proper access to water and sanitation
• http://www.who.int/inf-fs/en/fact112.html
Classification of water
• Ground water. Underground waters are
protected for just one use, as an actual or
potential source of drinking water. All ground
water is designated as Class 1.
• Surface water. All surface waters, lakes,
rivers, streams and wetlands in Minnesota are
either Class 2, protected for aquatic life and
recreation, or Class 7, designated as Limited
Resource Value Waters. In addition, all surface
waters (i.e., both Class 2s and 7s) are protected
for industrial use (Class 3), agricultural uses
(Class 4A and 4B), aesthetics and navigation
(Class 5), and other uses (Class 6). Thus, all
surface waters are protected for multiple uses.
• The detection of these
constituents in both raw water and
water delivered to consumers is
often slow, complex and costly,
which limits early warning
capability and affordability.
• Reliance on water quality
determination alone is insufficient
to protect public health.
As it is neither physically nor
economically feasible to test for all
drinking-water quality parameters
equally, monitoring effort and
resources should be carefully
planned and directed at significant
or key characteristics.
• Some characteristics not related to
health, such as those with significant
aesthetic impacts, may also be of
importance. Where water has
unacceptable aesthetic characteristics
(e.g. taste and odour), further
investigation may be required to
determine whether there are problems
with significance for health.
Verification
• Verification is the use of methods,
procedures or tests to determine if the
WSP is in compliance with the stated
objectives outlined by the water quality
targets and/or whether the WSP needs
modification and revalidation.
Verification of Microbial Quality
• For microbial quality, verification is
likely to include some microbiological
testing. In most cases will involve the
analysis of faecal indicator microorganisms, but in some countries this
may include assessment of pathogen
densities also.
• Approaches to verification could include
testing of source water, influents and
effluents of unit processes, treatment
end-point product and distribution
systems. Conventional faecal indicator
bacteria such as E. coli serves as the
primary indicator for verification
purposes, but at times and under certain
circumstances it may be desirable to
include more resistant microorganisms
such as bacteriophages, bacterial
spores.
• Such circumstances could include the
use of source water known to be
contaminated with enteric viruses and
parasites or high levels of viral and
parasitic diseases in the community.
• Since incremental improvement and
prioritizing action in systems presenting
greatest overall risk to public health are
important, there are advantages in
adopting a grading scheme for the
relative safety of supplies. More
sophisticated grading schemes may be
of particular use in community supplies
where the frequency of testing is low
and reliance on analytical results is
particularly inappropriate.
Verification of chemical
water quality
• Assessment of the adequacy of the
chemical quality of drinking-water
relies on comparison of the results of
water quality analysis with Guideline
Values.
• For most chemicals leading to adverse
effects after long periods of exposures
and arising from water sources, the
quality of water in supply is determined
by chemical analysis and compared
directly with tables of drinking-water
guidelines or national drinking-water
standards.
• For additives, i.e., chemicals deriving
primarily from materials and chemicals
used in the production and distribution
of drinking-water, emphasis is placed
on the direct control of additives, rather
than control of water in distribution.
• Some hazardous chemicals that occur
in drinking-water are of concern
because of effects arising from single
exposures or sequences of exposures
over a short period.
• Where the concentration of the
chemical of interest varies widely, even
a series of analytical results may fail to
fully identify and describe the public
health risk, for example nitrate which is
associated with methaemoglobinaemia
in bottle fed infants.
• In controlling such hazards, attention
must be given to both knowledge of
causal factors such as fertiliser use in
agriculture and trends in detected
concentrations since these will indicate
whether a significant problem may
arise in the future.
• Other hazards may arise intermittently,
often associated with seasonal activity
or seasonal conditions. Once example
is the occurrence of blooms of toxic
cyanobacteria in surface water.
Identifying priority water
quality parameters
• These Guidelines cover a large number
of constituents in drinking-water in
order to meet the varied needs of
countries world-wide.
• There are a large number of constituents
that may potentially occur in water.
Generally, only very few will be of
concern under any given circumstance.
It is essential that the national regulatory
agency and local water authorities
determine the relevance of constituents
in local drinking-water systems. This will
ensure efforts and costs can be directed
to those constituents that are of public
health relevance.
• Guidelines are established for
potentially hazardous water
constituents and provide a basis for
assessing drinking-water quality. It is
recognised that different parameters
may require different priorities for
management to ensure public health.
In general the progression of
priority is such that:
•
•
•
•
Ensure an adequate supply of
microbiologically safe water
Manage key inorganic contaminants
known to cause adverse health effects
in humans
Maintain acceptability of drinking-water
quality to prevent consumers seeking
other potentially less microbiologically
safe supplies
Address other chemical contaminants
Assessing microbial priorities
• The most common and widespread
health risk associated with drinkingwater is microbial contamination, the
consequences of which are such that its
control must always be of paramount
importance. It may be impossible to
attain the targets population-wide in the
short or medium term and it is therefore
necessary to ensure that priority is given
to improving and developing water
supplies to populations at greatest
public health risk.
• Microbial contamination of large
systems has the potential to affect a
large number of people through
potentially large outbreaks of waterborne disease. Improvement of quality
in such systems is therefore a priority.
• Nevertheless, the majority (around
80%) of the global population without
access to improved water supply is
rural. Similarly small and community
supplies in most countries contribute
disproportionately to overall water
quality concerns. Identifying local and
national priories should take factors
such as these into account.
Assessing chemical priorities
• The selection of chemicals for
consideration in the Guidelines for
Drinking-water Quality takes into account
the frequency and concentration that the
chemical is detected in drinking-water,
and/or those for which member states have
specifically requested guidance because of
a range of concerns. Guideline values are
developed for those chemicals considered
to be potentially hazardous to human
health and occur significantly at
concentrations of concern for public
health.
• The selection of chemicals for
consideration in the Guidelines for
Drinking-water Quality takes into account
the frequency and concentration that the
chemical is detected in drinking-water,
and/or those for which member states
have specifically requested guidance
because of a range of concerns. Guideline
values are developed for those chemicals
considered to be potentially hazardous to
human health and occur significantly at
concentrations of concern for public
health.
• Risk management efforts and
resources should give priority to those
chemicals in water systems that pose a
risk to human health, or to those with
significant aesthetic impacts.
• Only a few chemicals have been shown
to cause widespread actual health
effects in humans as a consequence of
exposure through drinking-water.
These should be addressed in all
circumstances in priority setting and
include fluoride, arsenic, nitrate and
lead.
• In some cases, assessment will
indicate that no risk of significant
exposure exists at national, regional or
system level. However, the scale of
health effects associated with these
chemicals indicates that they should be
considered under all circumstances.
Water, sanitation and health:
the current situation
• The prevailing worldwide situation
regarding water supply and sanitation
services is a source of concern in
different respects.
• Globally, some 1.1 billion people are
currently without access to improved
water supply and about 2.4 billion don't
benefit from any form of improved
sanitation services (figures for 2000).
The majority of these people live in
Asia and Africa. In Africa, for example,
two out of five people lack improved
water supply.
• Significant discrepancies between rural
and urban services continue to
contribute to the burdened life in rural
areas. On the other hand, the worldwide urbanization causes a great
number of people to live in informal,
overcrowded peri-urban settlements
where coverage remains especially low.
• Other points of concern are the
increasing pollution of both surface
and groundwater sources from
pesticides, industry and untreated
household waste waters.
• The over-extraction of water for
agriculture and manufacturing, which
causes the water table to decline in
many parts of the world, is another bad
practice which is producing severe
consequences to the sustainability of
these resources.
Water supply data at global level
• The percentage of people worldwide
who have access to an improved water
supply has risen from 78% in 1990 to
82% in 2000. Some 902 million more
people have been served during the
decade (537 million in urban and 365
million in rural areas).
• Data representing 94% of the Asian
population suggest that only 48% of the
population has sanitation coverage, by
far the lowest of any region of the
world. The situation is even worse in
rural areas, where only 31% of the
population has improved sanitation,
compared with 78% coverage in urban
areas.
• Total water coverage in Asia is also the
second lowest, after Africa, at 81%. But
again, water supply coverage is lower
in rural areas (75%) compared with that
in urban areas (93%).
• Because of the population sizes of
China and India, along with other large
nations in the region, Asia accounts for
the vast majority of people in the world
without access to improved services.
• Eighty percent of the global population
without access to improved sanitation,
and almost two-thirds without access to
improved water supply, live in Asia.
• At present, approximately one-third of
the Asian population is urban and twothirds live in rural areas. But this
balance is predicted to shift over the
coming decades. By the year 2015, the
urban population is projected to be 45%
of the region's total, and grow to just
over one-half of the total Asian
population by 2025.
• To meet the international development
target of halving the proportion of
people without access to improved
services by 2015, an additional 1.5
billion people in Asia will need to
access to sanitation facilities, while an
additional 980 million will need access
to water supply.
Water-related Diseases
• Potential water borne pathogens
• Bacteria
Vibrio cholerae
Shigella
Campylobacter
Francisella tularensis
Aeromonas
Legionella pneumophila
Salmonella
Toxigenic Escherichia coli
Leptospira
Yersinia enterocolitica
Helicobacter pylori
Viruses
• Protozoa
Norwalk and
Norwalk-like
Rotavirus
Hepatitis A and E
Giardia lamblia
Naegleria fowleri
Entamoeba histolytica
Isospora belli
Toxoplasma gondii
Cryptosporidium parvum
Acanthamoeba
Cyclospora cayetanensis
Ballantidium coli
Microsporidia
Typhoid and paratyphoid enteric fevers
• Typhoid and paratyphoid fevers are
infections caused by bacteria which are
transmitted from faeces to ingestion.
Clean water, hygiene and good
sanitation prevent the spread of
typhoid and paratyphoid. Contaminated
water is one of the pathways of
transmission of the disease
The disease and how it affects people
• Typhoid fever is a bacterial infection of
the intestinal tract and bloodstream.
Symptoms can be mild or severe and
include sustained fever as high as 39°40° C, malaise, anorexia, headache,
constipation or diarrhoea, rose-coloured
spots on the chest area and enlarged
spleen and liver. Most people show
symptoms 1-3 weeks after exposure.
Paratyphoid fever has similar symptoms
to typhoid fever but is generally a milder
disease.
The cause
• Typhoid and paratyphoid fevers are caused
by the bacteria Salmonella typhi and
Salmonella paratyphi respectively. Typhoid
and paratyphoid germs are passed in the
faeces and urine of infected people. People
become infected after eating food or
drinking beverages that have been handled
by a person who is infected or by drinking
water that has been contaminated by
sewage containing the bacteria. Once the
bacteria enter the person’s body they
multiply and spread from the intestines, into
the bloodstream.
Distribution
• Typhoid and paratyphoid fevers are
common in less-industrialized
countries, principally owing to the
problem of unsafe drinking-water,
inadequate sewage disposal and
flooding.
Scope of the Problem
• The annual incidence of typhoid is
estimated to be about 17 million cases
worldwide.
Interventions
• Public health interventions to prevent
typhoid and paratyphoid include:
• health education about personal
hygiene, especially regarding handwashing after toilet use and before food
preparation; provision of a safe water
supply;
• proper sanitation systems;
• excluding disease carriers from food
handling.
• Diarrhoea: about 4 billion cases per
year cause 2.2 million deaths, mostly
among children under five.
• Intestinal worms infect about 10% of
the population of the developing world
and, depending upon the severity of the
infection, lead to malnutrition, anaemia
or retarded growth
• Trachoma: about 6 million people are
blind from trachoma. Studies found
that providing improved water supply
could reduce the infection rate by 25%.
• Schistosomiasis: about 200 million
people are infected with
schistosomiasis. Studies found that
improved water supply and sanitation
could reduce infection rate by 77%.