EXPLICACIÓN DEL FLUJO DE FONDOS

Recommended actions:

a. Immediate investigative action must be taken if E. coli are detected.

b. Although E. coli is the more precise indicator of fecal pollution, the count of thermotolerant coliform bacteria is an acceptable alternative. If necessary, proper confir- matory tests must be carried out. Total coliform bacteria are not acceptable indicators of the sanitary quality of water supplies, particularly in tropical areas, where many bacteria of no sanitary significance occur in almost all untreated supplies.

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Environment and Health

41 Viral pathogens: Viruses associated with waterborne transmis-

sion are predominantly those that can infect the gastrointesti- nal tract and are excreted in the feces of infected humans (en- teric viruses).

Chemical Aspects

A number of chemical contaminants have been shown to cause adverse health effects in humans as a consequence of pro- longed exposure through drinking-water. However, this is only a very small proportion of the chemicals that may reach drink- ing-water from various sources.

The presence of certain chemicals in excess of prescribed limits may constitute ground for rejection of the water as a source of public water supply.

These are:

Arsenic: Levels in natural waters generally range between 1

and 2 mg/liter, although concentrations may be elevated (up to 12 mg/liter) in areas containing natural sources.

Provisional guideline: 0.01 mg/liter

Barium: Barium is present as a trace element in both igneous

and sedimentary rocks, and barium compounds are used in a variety of industrial applications. However, barium in water comes primarily from natural sources.

Guideline value: 0.7 mg/liter

Benzene: Concentrations in drinking-water are generally less

than 5 mg/liter. Benzene is used principally in the production of other organic chemicals. It is present in petrol, and vehicu- lar emissions constitute the main source of benzene in the en- vironment. Benzene may be introduced into water by indus- trial effluents and atmospheric pollution.

Guideline value: 0.01 mg/liter

Cadmium: Occurrence levels in drinking-water is usually less

than 1 mg/liter. Cadmium metal is used in the steel industry and in plastics. Cadmium compounds are widely used in bat- teries. Cadmium is released to the environment in wastewater, and diffuse pollution is caused by contamination from fertiliz- ers and local air pollution. Contamination in drinking-water may also be caused by impurities in the zinc of galvanized pipes and solders and some metal fittings. Food is the main source of daily exposure to cadmium. The daily oral intake is 10–35 mg. Smoking is a significant additional source of cad- mium exposure.

Guideline value: 0.003 mg/liter

Chlorine: Chlorine is produced in large amounts and widely

used both industrially and domestically as an important disin- fectant and bleach. In particular, it is widely used in the disin- fection of swimming pools and is the most commonly used disinfectant and oxidant in drinking-water treatment. Present in most disinfected drinking-water at concentrations of 0.2–1 mg/liter

Guideline value: 5 mg/liter

Chromium: Chromium is widely distributed in the Earth’s crust.

Total chromium concentrations in drinking-water are usually

Table 4.1: Waterborne pathogens

Bacteria

Burkholderia pseudomallei Campylobacter jejuni, C. coli Escherichia coli – Pathogenic E. coli – Enterohemorrhagic Legionella spp. Non-tuberculous mycobacteria Pseudomonas aeruginosae Salmonella typhi Other Salmonellae Shigella spp. Vibrio cholerae Yersinia enterocolitica Viruses Adenoviruses Enteroviruses Hepatitis A virus Hepatitis E virus

Noroviruses and sapoviruses Rotaviruses Protozoa Acanthamoeba spp. Cryptosporidium parvum Cyclospora cayetanensis Entamoeba histolytica Giardia intestinalis Naegleria fowleri Toxoplasma gondii Helminths Dracunculus medinensis Schistosoma spp.

Table 4.2: Guideline values for coliform bacteria

Organisms Guideline value

All water directly intended for drinking

E. coli or thermotolerant Must not be detectable coliform bacteria-sample in any 100 ml Treated water entering the

distribution system

E. coli or thermotolerant Must not be detectable coliform bacteria-sample in any 100 ml Treated water in the

distribution system

E. coli or thermotolerant Must not be detectable coliform bacteria-sample in any 100 ml

c. It is recognized that in the great majority of rural water supplies, especially in developing countries, fecal contami- nation is widespread. Especially under these conditions, medium-term targets for the progressive improvement of water supplies should be set.

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less than 2 mg/liter, although concentrations as high as 120 mg/liter have been reported.

Provisional guideline value: 0.05 mg/liter for total chromium [provisional because of uncertainties in the toxicological database].

Cyanide: Cyanides can be found in some foods, particularly in

some developing countries, and they are occasionally found in drinking-water, primarily as a consequence of industrial con- tamination.

Guideline value: 0.07 mg/liter

Fluoride: Fluoride accounts for about 0.3 g/kg of the Earth’s

crust and exists in the form of fluorides in a number of miner- als. The most important source of fluoride in drinking-water is naturally occurring. Fluorosilicic acid, sodium hexafluorosilicate and sodium fluoride are used in municipal water fluoridation schemes. Daily exposure to fluoride depends mainly on the geographical area. In most circumstances, food seems to be the primary source of fluoride intake, with lesser contributions from drinking-water and from toothpaste. In groundwater, con- centrations vary with the type of rock the water flows through but do not usually exceed 10 mg/liter; the highest natural level reported is 2800 mg/liter.

Guideline value: 1.5 mg/liter

Iron: Iron is one of the most abundant metals in the Earth’s

crust. It is found in natural fresh waters at levels ranging from 0.5 to 50 mg/liter. Iron may also be present in drinking-water as a result of the use of iron coagulants or the corrosion of steel and cast iron pipes during water distribution. Iron is an essen- tial element in human nutrition. Estimates of the minimum daily requirement for iron depend on age, sex, physiological status and iron bioavailability and range from about 10 to 50 mg/day.

No guideline value for iron in drinking-water is proposed.

Lead: Lead is used principally in the production of lead-acid

batteries, solder and alloys. Owing to the decreasing use of lead containing additives in petrol and of lead containing sol- der in the food processing industry, concentrations in air and food are declining, and intake from drinking-water constitutes a greater proportion of total intake. Lead is rarely present in tap water as a result of its dissolution from natural sources rather, its presence is primarily from household plumbing systems con- taining lead in pipes, solder, fittings or the service connections to homes. The amount of lead dissolved from the plumbing system depends on several factors, including pH, temperature, water hardness and standing time of the water. Concentra- tions in drinking-water are generally below 5 mg/liter, although much higher concentrations (above 100 mg/liter) have been measured where lead fittings are present.

Guideline value: 0.01 mg/liter

Mercury: Mercury is mainly used in the electrolytic production

of chlorine, in electrical appliances, in dental amalgams and as a raw material for various mercury compounds. Mercury is

present in the inorganic form in surface water and groundwater at concentrations usually below 0.5 mg/liter, although local mineral deposits may produce higher levels in groundwater. Food is the main source of mercury in non-occupationally exposed populations. The mean dietary intake of mercury in various countries ranges from 2 to 20 mg/day per person.

Guideline value: 0.006 mg/liter for inorganic mercury

Radiological Aspects

The effects of radiation exposure are called somatic if they become manifest in the exposed individual, and hereditary if they affect the descendants. Malignant diseases is the most important somatic effect.

Radiation exposure through drinking-water

Radioactive constituents of drinking-water can result from: • Naturally occurring radioactive species (e.g. radionuclides

of the thorium and uranium decay series in drinking-wa- ter sources), in particular radium-226/228 and a few oth- ers

• Technological processes involving naturally occurring ra- dioactive materials (e.g. the mining and processing of mineral sands or phosphate fertilizer production) • Radionuclides discharged from nuclear fuel cycle facili-

ties

• Manufactured radionuclides (produced and used in un- sealed form), which might enter drinking-water supplies as a result of regular discharges and, in particular, in case of improper medical or industrial use and disposal of ra- dioactive materials

• Past releases of radionuclides into the environment, in- cluding water sources.

HARDNESS OF WATER

Hardness may be defined as the soap-destroying power of water. It is mainly caused by

1. Calcium bicarbonate 2. Magnesium bicarbonate 3. Calcium sulfate

4. Magnesium sulfate

Table 4.3: Classification of hardness in water

Classification Level of hardness (mg /liter)

(a) Soft water Less than 1(<50 mg/L) (b) Moderately hard 1-3(50-150 mg/L)

(c) Hard water 3-6(150-300 mg/L)

(d) Very hard water over 6 (>300 mg/L)

Hardness is classified as: (i) carbonate or “temporary” hardness and (ii) non-carbonate or “permanent” hardness. The carbonate hardness is due to the presence of calcium and magnesium bicarbonates. The noncarbonated hardness is due to calcium and magnesium sulfates, chlorides and nitrates (Table 4.3).

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Environment and Health

43

SPECIAL TREATMENT OF WATER

1. Removal of hardness

Temporary hardness

a. Boiling

b. Addition of lime

c. Addition of sodium carbonate d. Permutit process

Permanent hardness

a. Addition of sodium carbonate b. Base Exchange process 2. Fluoridation of water

Water fluoridation is the practice of adding fluoride com-

pounds to water with the intended purpose of reducing

tooth decay in the general population. Many North Ameri- can and Australian municipalities fluoridate their water

supplies in the belief that this practice will reduce tooth decay at a low cost. Currently 66 percent of United States residents on public water supplies have fluoridated wa- ter.

Typically fluoride is added in the form of sodium hexafluorosilicate or hexafluorosilicic acid, at a level be- tween 0.7 and 1.2 ppm.

3. Defluoridation

Fluoride, as a dissolved constituent of drinking water, is perhaps the only substance producing divergent health effects on the consumer depending upon their relative proportions. While a fluoride concentration in the range of 0.8 to 1.20 mg/liter is considered to be beneficial, con- centration higher then 1.5 mg/liter are reported to be harmful to the teeth and bone structure of men and ani- mals. The necessity of removal of excess fluoride has led to development of several defluoridation methods. Most of these methods are based upon ion exchange process, adsorption or addition of chemicals to water during treat- ment. Defluoridation is a process of removal of fluoride ion in drinking water. The different methods so far tried for the removal of excess fluoride from water can be broadly classified into four categories. Viz

a. Adsorption method b. Ion Exchange method c. Precipitation method

d. Miscellaneous method. (e.g. Reverse Osmosis)

AIR

The immediate environment of man comprises of air on which depends all forms of life. Apart from supplying the life giving oxygen, air and atmospheric conditions serve several functions.

Composition

Nitrogen 78.1 percent Oxygen 20.93 percent Carbon dioxide 0.03 percent

Other gases in traces: e.g. argon, neon, krypton, xenon and helium. In addition to these gases, air also contains water vapor, traces of ammonia and suspended matter such as dust, bacteria, spores and vegetable debris.

Air Pollution

The term Air Pollution signifies the presence in the ambient atmosphere of substances generated by the activities of man in concentrations that interfere with human health, safety or comfort,or injurious to vegetation and animals and other environmental media resulting in chemicals entering the food chain or being present in drinking water and thereby constituting additional source of human exposure.

In document FONCAIXA PYMES 4, FONDO DE TITULIZACIÓN DE ACTIVOS EMISIÓN DE BONOS DE TITULIZACIÓN EUROS (página 164-184)