State of the Environment Report 2007
Environmental health is classed as an emerging issue because there is currently inadequate information to report fully on this issue: environmental conditions can affect human health and in many instances the links between the two are not well understood. Environmental health is the relationship of human health to environmental factors including water, air, food, contaminated land, waste management, vector-borne disease and the built environment. Environmental changes arising from urbanisation, population increases, and industrial and agricultural activities have resulted in reduced quality of air, water and soil and a greater presence of persistent chemical pollutants. Environmental degradation and chemical overload can be linked to diseases such as respiratory and cardiovascular disease, neurological and physiological disorders, and increased incidence of many cancers.
Although it can be demonstrated that disease and death occur without environmental health safeguards, direct causal links between specific environmental factors and particular disease outcomes are often not well understood and are difficult to show. Some direct relationships have been established, for example between toxic algal blooms and water-borne disease. Another link, between urban form and motor vehicle use, and obesity and heart disease has been demonstrated. It is more difficult to show a direct relationship between a particular substance in the environment and diseases such as asthma or lung cancer (these illnesses can have other causal roots such as genetic predisposition, exposure to cigarette smoke or lifestyle). Many environmental issues discussed in this report, including the three examples which follow, have impacts on human health.
1. Vector-borne diseases are caused by pathogens transmitted from infected to susceptible hosts via the bite of vector organisms. Vectors are usually arthropods (insects and insect-like organisms) including biting flies, mosquitoes and ticks. They transmit a diverse array of pathogens including viruses (e.g. arboviruses), protozoa (e.g. malaria) and nematode worms (e.g. lymphatic filariasis). In WA, the vector-borne diseases of greatest concern to public health are mosquito-borne viruses including Ross River virus and Barmah Forest virus. These viruses occur statewide, but are most prevalent in coastal areas of the South West, and in the Kimberley and Pilbara regions. They cause non-fatal but potentially debilitating symptoms, which may persist for weeks or months. An average of well over 1000 cases of Ross River virus has been reported for each of the last three major outbreaks in WA. In the Kimberley and Pilbara, the rarer but potentially fatal Murray Valley encephalitis virus is a public health concern. There are no cures or vaccines for these native mosquito borne diseases.
Mosquitoes have successfully colonised a vast array of natural and artificial water bodies. The current trend in WA of building new residential subdivisions in close proximity to inland waters and artificial wetlands, has resulted in a much larger human population residing in high-risk environments. This conflict between public health risk and 'desirable' real estate has been particularly evident during recent major outbreaks of Ross River virus. Of the 805 rural South West cases reported in 2003-04, 627 were in communities around major coastal waterways in the Peel, Leschenault, Capel and Busselton regions. The majority of 488 cases reported from Perth during the same outbreak were from outer semi-rural suburbs or suburbs with natural or artificial wetlands. Clear relationships between distance from water bodies and number of cases of Ross River virus during major outbreaks are evident from an earlier outbreak in the Peel Region (e.g. Figure HS6.1). This highlights the importance of planning for adequate buffers around waterways and wetlands.
In addition to the burden on human health, mosquito-borne diseases have substantial economic costs, including costs of health care, lost productivity, and negative impacts on tourism and real estate values (Commonwealth of Australia, 1999). The nuisance caused by biting insects, especially mosquitoes, can impact severely on quality of life for communities in affected areas.
![Figure HS6.1: Cases of Ross River virus (in one kilometre zones from waterways) in the Peel region, including the Murray and Serpentine rivers, 1995-98. [Data source: Department of Health.]](/site/files/images/Figure-HS6.1_Large.jpg)
2. Allergic and respiratory diseases affect a significant proportion of the community, with one in five households affected by respiratory disease and more than 30% of the community having an allergic disorder. There has been a rapid increase in allergic diseases in the last 30 years, an epidemic seen only in western societies. This is likely to be directly related to the impact of human settlements on our environment and on disease. Causal links between environmental factors and some respiratory or allergic diseases have been established. For example, the number of cardiorespiratory deaths in Australia is directly proportional to the level of small particulates in city air (Simpson et al., 2005). Exposure to air pollutants has been linked to several other diseases including adenocarcinoma, emphysema, chronic bronchitis, pneumonia, Legionnaire's disease and sick-building syndrome.
Both indoor and outdoor air quality have a considerable influence on lung and allergic diseases, many of which are caused by multiple environmental factors. An example is asthma, a chronic disease that has serious health effects and if uncontrolled leads to permanent lung damage. Grass pollens, such as rye and oats, are blown into settlements from surrounding rural areas and are a common trigger factor (allergen) for asthma (Burton et al., 2002). Outdoor air pollutants, such as those from vehicle exhaust emissions, can exacerbate asthma enhancing allergic responses and converting some pollen proteins (e.g. birch pollen) into allergens. Childhood asthma rates are higher for those who live near major traffic corridors (Brauer et al., 2002). Indoor allergens such as house dust mites, cats, cockroaches, moulds and gases trapped in the home are also common triggers for asthma (D'Amato et al., 2005), and are exacerbated by housing design which encourages poor ventilation and low air exchange rates. Occupational asthma constitutes 5-10% of all asthma, with over 350 known causative agents in the workplace (American Thoracic Society, 2003).
Respiratory diseases have a significant socio-economic impact. For example, 10% of adults and 20% of children are affected by asthma in Australia (Australian Centre for Asthma Monitoring, 2005), which costs the nation nearly $1 billion annually (Australian Centre for Asthma Monitoring, 2001). This figure is matched only by the cost of emphysema and chronic bronchitis (Australian Lung Foundation, 2002).
3. The health of Aboriginal people in WA is much poorer in general than the health of the non-Aboriginal population, with higher rates of infectious illness, chronic diseases and disability, and life expectancies around 15 to 20 years lower. The state of Aboriginal living environments is a contributing factor to poor health. Many Aboriginal people living in remote and town-based communities in WA do not enjoy the same standard of environmental health infrastructure (such as power, water and waste removal services) as people living in cities and major towns. This affects capacity to implement healthy living practices in these communities. A recent environmental health survey (Environmental Health Needs Coordinating Committee, 2005) of 274 discrete Aboriginal communities (those inhabited by Aboriginal people and with community-owned housing or infrastructure) showed that 73% use bore water and 58% of smaller communities have untreated water. Fifty per cent of the communities using septic tanks reported being without pump-out equipment for maintenance, and 80% of communities also lacked a dust suppression program.
Hospital morbidity data (2000-2004) show that patient discharges for influenza, pneumonia and intestinal infectious diseases were six times higher for Aboriginal people than for the non-Aboriginal population, and acute upper respiratory infections were 4.5 times higher (Department of Indigenous Affairs, 2005). These conditions have been linked to the state of living environments. Many infectious illnesses are preventable if people have basic healthy living practices. Aboriginal housing surveys in rural and remote communities in WA showed that in a sample of 469 houses 25% had working showers; 40% had working basins, baths or tubs; 25% had functioning facilities to wash clothes and bedding; 50% had functioning flush toilets; 7% had all drains working; and only 3% had kitchens enabling storage, preparation and cooking of food (Healthabitat Pty Ltd, 2005). Equipment problems were mainly due to faulty installation and lack of regular maintenance.
Reduced health of Aboriginals in remote and regional towns can have substantial social and economic impacts, including reduced life expectancy, quality of life, and settlement productivity and viability.
