It is well known that the environment influences our health in many ways — through exposures to physical, chemical and biological risk factors, and through related changes in our behaviour in response to those factors. However, the significant question is how much is the contribution of environment in disease and if one better manages his or her environment, how much disease could be prevented?
Trying to answer this issue, the World Health Organisation (WHO) way back in 2002, undertook a study across in 14 regions worldwide and separately for children, by summarising scientific evidence and consultation with more than 100 experts for estimates on how much environmental risk factors contributes to a category of 85 diseases and injuries.
The study confirmed that an estimated 24 per cent of the disease burden (healthy life years lost) and an estimated 23 per cent of all deaths (premature mortality) was attributable to environmental factors. Among children 0–14 years of age, the proportion of deaths attributed to the environment was as high as 36 per cent.
A concept ‘the Disability-Adjusted Life Year’ (DALY), indicating total number of years of healthy life lost was developed for measuring the burden. The DALY measure generally combines morbidity (Years Lived with Disability-YLDs) and mortality (Years of Life Lost-YLLs) in one measure and thus enables the comparisons of different diseases, interventions, populations, and periods.
The Environmental Burden of Disease (EBD) is defined as the number of DALYs that can be attributed to environmental factors. Thus, EBD allow for comparison of disease burdens, and could be very effective management tool to forecast the possible impacts of health or environmental interventions. The WHO studies pointed out that, diarrhoea, lower respiratory infections, other unintentional injuries and malaria are diseases with the largest absolute burden attributable to modifiable environmental factors.
An estimated 94 per cent of the diarrhoeal burden of disease is attributable to environment and associated with risk factors such as unsafe drinking-water and poor sanitation and hygiene. Lower respiratory infections, in second place, are related with air quality – largely to household solid fuel use and possibly to second-hand tobacco smoke, as well as to outdoor air pollution.
About 44 per cent of respiratory infections are attributable to environmental causes in developing countries. Around 44 per cent other unintentional injuries such as injuries arising from workplace hazards, radiation and industrial accidents, are attributable to environmental factors. Some 42 per cent of malarial incidences are attribu-table to modifiable environmental factors, associated with policies and practices of land use, deforestation, water resource management, modified house design, improved drainage etc.
In India, water, sanitation and hygiene (with reference to diarrhoea only) causes about 4,54,400 deaths, indoor air quality results in 4,88,200 premature deaths while, outdoor air with respirable particulate matter results in 1,19,900 pre- mature deaths. Cumulatively, Indian environmental burden of disease results in 26,91,800 deaths per year. In terms of EBD, we stands at 65th position, while the lowest is 13 and highest 289 with an environmental burden of disease at 24 per cent.
Unhealthy behaviour
At the same time, EBD also indicates that potential benefits of better environmental management. Modifiable environmental factors are those conditions that are realistically amenable to change using available technologies, policies, and preventive and public health measures. These environmental factors include physical, chemical and biological hazards that directly affect health and also increase unhealthy behaviour (reduced physical activity).
For instance, it has been estimated by the WHO in 2004 that providing safe drinking water and improved sanitation to a developing country household would result in an average gain of 60 minutes per household per day, in terms of time spent collecting water. Safe sanitation also helps break the cycle whereby faecal-oral pathogens often infiltrate drinking water.
Consequent reductions in environmental pollution can not only benefit households, but also fisheries, the food industry, those engaged in water-based recreational activities, as well as the health sector (from avoided healthcare costs), and the labour sector (from fewer work days lost to illness).
The EBD studies indicate that air pollution is the fifth leading cause of death in India after high blood pressure, indoor air pollution, tobacco smoking, and poor nutrition. About 6,20,000 premature deaths occur from air pollution related diseases. This represents a six-fold increase. It is also the seventh leading cause behind the loss of about 18 million healthy years of life due air to illness.
Measuring EBD on either exposure to three selected risk factors of unsafe water/sanitation, indoor air pollution due to solid fuel use, outdoor particulate matter, or using ‘Total Environmental Burden of Disease’ – regional exposure based on Comparative Risk Assessment – can provide useful polity inputs. This will ensure better environment-health linkages and any decisions that could have influence on environmental burden of disease should be an informed decision.
(The writer is associated with Karnataka State Women’s University, Vijayapura, Karnataka)