Health aspects of urban sanitation

by Han Heijnen

WHO, on the basis of BBS data, estimated in 1999 the urban population in Bangladesh to be around 34 million. A good number of these urban dwellers have come to the urban areas, and in particular Dhaka and Chittagong, in search of work and opportunity to improve their lives. Many have hardly any resources to start a new life and so they are often forced to stay in the margin of the city, in the slums. How many people are deemed to live in slums is probably a matter of definition. When considering living space, access to basic facilities and a feeling of protection, it is fair to say that 40-50 per cent of the population in the large agglomerations is living in slum-like conditions that endanger their health and well-being. Lack of access to adequate sanitation, safe water and clean air leads to a disease burden that is directly linked to the way people are forced to live.

The total diseases burden due to the hygiene, sanitation and water related diseases: 17.9 +14.8 = 32.7 and due to the diseases associated with cramped living conditions and (indoor) air pollution: 34 per cent thus forms two-third of all diseases reported. Most sanitation-related infections are faecal-oral. This means that their transmission route is from the faeces of an infected person into the mouth of another person. Pathogens are the ineffective organisms excreted by an already infected person, which can then enter the body of another person and infect him or her. Pathogens may be viruses, bacteria or small worm. A vector is the organism by which a disease is transmitted from one person to another. Mosquitoes are vectors of malaria, dengue and filariasis. Helminths are small piratical worms that live in the body, usually in the gut, and make people feel tired and listless. 

In recent years important insight has been gained with respect to the transmission of disease associated with water and sanitation. The faecal-oral route is the most important through contaminated water (fluids) and poor hygiene (fingers-no handwashing). 

To break the cycle of transmission for the faecal-oral group of diseases it is nowadays accepted that sanitary disposal of human faeces (including final disposal or treatment), having clean water for handwashing and keeping utensils clean, and keeping drinking water free from faecal contamination are minimum requirements to avoid diarrhoeal diseases, such as dysentery, giardiasis, or shigellosis.

It is also agreed that good hygiene requires a regular bath, so adequate water of reasonable quality should be available. The high incidence of water-washed diseases in slum areas points, to a lack of sufficient water or opportunity to take a bath. Skin infections and eye irritations are consequence.

Sufficient dean water and a clean place to prepare and store (prepared) food are also very much necessary to avoid the risk of food poisoning. Many homes in the slums do not offer a convenient place to prepare food, and so it is done in the open, over a drain, with dogs and chickens running about and everything that floats in the air settling on the food.

People live in cramped conditions, with high levels of air pollution in their homes, with children exposed to smoking adults in the same room, and with all respiratory diseases well sprayed around. Damp humid sleeping areas and insufficient ventilation leads to a high prevalence of coughs and colds, and subsequently of respiratory diseases.

Whereas many diseases are linked to the family unit, the household, poor sanitation by some will also affect the others living nearby and even further away. Poor sanitation keeps pathogens in circulation. Depending on circumstance they can spread through animals (dogs, rats, chicken) who rummage through the stool and the solid waste aggregating and putrefying in the drains, through rainfall run off and floods and through vectors like mosquitoes carrying dengue. In that respect disease does not stop at the doorstep of the better off. They will also feel the brunt of the vector borne diseases if their drains are not kept dean and solid wase management is neglected.

For that reason the public health authorities should consider sanitation as a municipality-wide concern where everyone may be affected by poor sanitation, poor solid waste management poor hospital waste management and management of other hazardous waste produced when slaughtering animals, and poor drainage. It does also need a combined approach with households and wards taking primary responsibility for their safe sanitation, but municipal authorities providing the means to assist at all levels and to integrate solutions into a larger and sustainable, environmentally sound waste management system.

The objective of sanitation and sanitation-related activities such as hand-washing is to break the transmission routes so that pathogens from an infected person cannot be transmitted to an other person It is riot sufficient to break one route if the others are still open. This means that one must approach questions of sanitation and hygiene in an integrated way.

Sanitation plans should also emphasize the need to provide a source of water close to each latrine so that people can wash their hands after defecating.

Sanitation assumes that the management cycle is complete, that is that the production and storage of human waste, is followed by collection and transport and ultimately decentralized or centralized treatment and disposal. Where there are shortcomings in the cycle, risks of pollution may have serious consequences for public health and bacteriological contamination appear that may have serious consequences for public health.

Poor solid waste collection encourages disease transmission. Uncollected solid waste in streets or at dumpsites can provide a habitat for rats and flies and thus contribute to the spread of a number of diseases. Rats are the major vectors of plague, leptospirosis and other infections while flies provide a possible transmission route for faecal-oral disease.

Discarded tin cans and tyres can collect relatively clean water and thus provide a breeding ground for Aedes mosquitoes, which transmit dengue and yellow fever.

Uncollected solid waste often finds its way into surface drains and sewers, causing blockages, contributing to flooding and helping to create insect breeding sites. All these impacts can be reduced by improvements in solid waste management. However localised improvements will not eliminate problems. If waste is collected in some streets but not in the surrounding areas, there is nothing to stop insects and rats crossing from one area to another and carrying diseases with them. This reinforces the point that sanitation improvements need to be citywide.

New sanitation facilities do not automatically lead to improvements in health. Poorly maintained facilities can actually make the situation worse and lead to deterioration in health.

The effect of sanitation improvements on health will be limited unless they are accompanied by efforts to improve hygiene. Good hygiene requires water so there should be a source of water close to every sanitation facility so that people can wash their hands after defecating.

Young people are more susceptible to many sanitation-related diseases than older people. This is because the latter have built up immunity over time. It is important to ensure that all, including children, use sanitation facilities.

The faeces of children are as infective as those of adults. Hygiene promotion materials should emphasise this point since many people believe that the faeces of children are harmless.

The most significant impacts on health are likely to come from improvements at the household level where people spend most of their time and are most likely to encounter pathogens.

Improvements in public facilities will have little impact unless they are linked with improvements within the household.

Improvements in sanitation will have the greatest effect in densely populated urban areas where the amount of faecal material produced is the greatest and the difficulties in removing it are greatest.

The author is the Environmental Health Advisor, WHO Bangladesh.

Source: The Independent, April 1,2001