Health Aspects of Water Supply Flashcards
Two major qualities of water
Chemical (generally of lower importance; more time for remedial action)
MIcrobiological (outbreaks and epidemics; may have immediate adverse health effects)
Water related diseases are related to
impurities in water
*infectious/non-infectious
Disease transmitted through ingestion of contaminated water leading to diarrheal disease (cholera, typhoid fever, hepatitis, amoebiasis, cryptosporidiosis)
Water-borne diseases
Transmissions of water-borne diseases
Classical Water-borne infection cycle (demonstrates role of water contamination in transmission of water-borne diseases)
Fecal-oral route (exhibits the actors that contribute to transmission)
Water-borne infection cycle
Infected person > pathogens in excreta > contaminated water source > consumption of untreated water > susceptible person >
Ways by which individuals acquire disease
Ingestion of contaminated water
Hand-to-mouth habit
Why are children most vulnerable to fecal-oral route of transmission of water-borne diseases
- Consistent hand-to-mouth habit
2. Unwariness of what they are eating/drinking
why undertaking studies on the health impact of improvements in water supply quality is difficult
Infection have several and multiple routes
Prevention strategies for water-borne diseases
- Improve drinking wate quality through treatment
- Prevent use of unprotected sources (by discouraging use of springs, traditional wells, and open ponds)
- Proper disposal of human waste
Treatment of drinking water
• Coagulation • Flocculation • Sedimentation • Filtration • Disinfection → Must be ensured → Only process that directly addresses problems in microbiological quality
Low-risk water sources
→ Fully enclosed or protected (capped) and no surface water can run directly into it
→ People do not step into the water while collecting it
→ Latrines are located as far as possible, preferably not on higher ground
(Waters may leech by means of gravity)
→ Solid waste pits, animal excreta, and other pollution sources are located as far as possible
→ No stagnant water within 5 meters from the source
→ Wells: buckets are kept clean and off the ground, or a handpump is used
One of the principal ways of breaking the fecal-oral cycle
Safe disposal of feces
A critical barrier to disease transmission
Adequate sanitation
T or F: In water-washed diseases, transmission depends on quantity of water used rather than quality
True
Two main types of water-washed diseases
→ Infection of the eyes and skin (scabies, fungal infections, trachoma)
→ Infection carried by lice (louse-borne epidemic typhus)
What causes scabies?
Sarcoptes scabiei
common symptoms of scabies
intense itching and a pimple-like skin rash
• Usually spread by direct skin-skin contact with a person who has scabies
→ Scabies can spread rapidly under crowded conditions where close body contact is frequent
What causes trachoma?
*repeated infection = scarring
Chlamydia trachomatis (spread p to p through discharge from infected child's eyes) *blindness does not happen until adulthood
louse-born epidemic typhus is caused by
Rickettsia prowazekii
How is louse-borne epidemic typhus transmitted?
- Transmitted by body lice and cannot persist on people who regularly wash their clothes
- Can be due to limited access to water for regular bathing
Disease prevented by increasing water quantity used and improving accessibility and reliability of domestic water supply
Louse-born epidemic typhus
- Pathogen spends part of its life-cycle in water (e.g. snail or other aquatic animals)
- Parasitic worms require intermediate hosts to complete their life cycles
Water-based diseases
A water-based disease which is a major public health problem wherein miracidium enters snail in water
Schistosomiasis
How is schistosomiasis acquired?
when people come in contact with fresh water infested with larval forms (cercariae) of parasitic blood flukes, known as schistosomes
Advanced stages of schistosomiasis involves
enlargement of liver or spleen
Where is schistosomiasis prevalent?
tropical and sub-tropical area
How is schistosomiasis prevented?
- Reduce contact with infected water
2. Reduce snail population
These are spread by insects which either breed in water or bite near water (i.e.: malaria, DF, filariasis)
Water-vectored diseases
Prevention of water-vectored diseases
- Destroy breeding sites of insects
- Environmental modification (canal/drains)
→ Water will flow faster in canals made up of cement rather than soils. Thus, this prevents insect breeding since they prefer stagnant waters
→ Piped drains instead of open drains - Reduce the need to visit breeding sites
- Use mosquito netting
How can the chemistry of water lead to disease?
→ Absence or deficiency of a necessary constituent (not generally a problem because of alternative sources)
→ Excess of a harmful chemical
This causes poor growth of bones and teeth in the young
Fluoride deficiency
→ Higher incidence of dental caries
Organic harmful chemicals
micropollutants (less than 1 ug/L)
*Some are toxic or carcinogenic or produce odor/taste after reacting with chlorine
Organic chemicals which are toxic or carcinogenic or produce odor/taste after reacting with chlorine are by-products of what
disinfection
Organic chemicals which may be present in concentration between 1-100 ug/L (except chloroform which can exceed this)
Trihalomethanes
- by-product of chlorine disinfection wherein chlorine reacts with precursor organics from decaying matter
- carcinogenic animals
Examples of inorganic harmful chemicals include
metallic ions – mercury, lead, cadmium, vanadium
More significant problem wrt inorganics in developing countries
the effect of salts in ground water – mainly chlorides and sulfates which makes the water unpalatable
harmful chemical from sedimentary deposits deriving from volcanic rocks
Arsenic
Effects of arsenic
Dermal lesions will appear after having at least 5 years of exposure
Affects CVS of children
harmful chemical which is primarily from corrosive water effects on househould plumbing system
Lead
Why is pH included as a mandatory (also operational) parameter?
it detects the presence of other contaminants.
- extremely alkaline = contaminated with pollutants
- acidic = heavy metals
Effects of lead
- neurodevelopment effects in children (decrease of at least 3 IQ points)
- Increase in systolic bp of approximately 3 mmHg in adults
What causes methemoglobinemia among infants?
nitrates reduced to nitrites
most affected population wrt to nitrate excess
Bottle-fed infants
Sources of nitrate
*PNSDW: 50 mg/L
→ Industrial pollution
→ Can be from agricultural activity (excessive fertilizers/manures)
→ Wastewater disposal
→ Waste from septic tank
→ Surface or ground waters receiving organic pollution have high nitrate levels
A discharge from mining industry which causes severe kidney damage due to increased urinary excretion of total protein, glucose and amino acids
Cadmium
*causes disturbance of Ca/P reabbsorption = bone softening
Disease due to excessive exposure to cadmium
Itai-Itai disease
A branch of DTI that prescribes certain levels in all products, including pipes that can be used that contains minimum metals
Bureau of Products Standards
categories of sources of chemical constituents
see trans for examples
Natural
Industrial sources and human dwellings
Agricultural activities
Water treatment or materials in contact with drinking water
Pesticides used in water for public health
