Drinking water Drinking water and health and health

Luiza GharibyanLuiza Gharibyan Associate professor of Yerevan Associate professor of Yerevan

State Medical UniversityState Medical UniversityDepartment Hygiene and EcologyDepartment Hygiene and Ecology

WHO Water/Health FactsWHO Water/Health Facts

• Every 8 seconds a child dies of water-related 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 waterClassification 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.

VerificationVerification

• 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 QualityVerification of Microbial Quality

• For microbial quality, verification is likely to include some microbiological testing. In most cases will involve the analysis of faecal indicator micro-organisms, 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 Verification of chemical water qualitywater 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 Identifying priority water quality parametersquality 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 In general the progression of priority is such that: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 prioritiesAssessing microbial priorities • The most common and widespread health

risk associated with drinking-water 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 water-borne 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 prioritiesAssessing 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: Water, sanitation and health: the current situation 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 world-wide 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 levelWater 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 two-thirds 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 DiseasesWater-related Diseases • Potential water borne pathogens• Bacteria

Vibrio choleraeShigella CampylobacterFrancisella tularensisAeromonas Legionella pneumophilaSalmonellaToxigenic Escherichia coliLeptospiraYersinia enterocoliticaHelicobacter pylori

• Protozoa

Giardia lambliaNaegleria fowleriEntamoeba histolyticaIsospora belliToxoplasma gondiiCryptosporidium parvumAcanthamoebaCyclospora cayetanensisBallantidium coliMicrosporidia

Viruses

Norwalk and Norwalk-likeRotavirusHepatitis A and E

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 peopleThe 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 causeThe 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.

DistributionDistribution

• 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 ProblemScope of the Problem

• The annual incidence of typhoid is estimated to be about 17 million cases worldwide.

InterventionsInterventions

• Public health interventions to prevent typhoid and paratyphoid include:

• health education about personal hygiene, especially regarding hand-washing 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%.