Development, and industrialization in particular, have made immense positive contributions to health, including greater personal and social wealth, as well as vastly improved health and education services, transportation and communication. Unquestionably, on the global scale, people are living longer and are healthier than they were centuries and even decades ago. However, industrialization has also had adverse health consequences not only for workforces, but for the general population as well. These effects have been caused either directly by exposure to safety hazards and harmful agents, or indirectly through environmental degradation locally and globally (see “Industrial pollution in developing countries” in this chapter).

This article outlines the nature of environmental health hazards and the reasons for linking environmental health with occupational health.

Environmental health hazards, like occupational health hazards, may be biological, chemical, physical, biomechanical or psychosocial in nature. Environmental health hazards include traditional hazards of poor sanitation and shelter, as well as agricultural and industrial contamination of air, water, food and land. These hazards have resulted in a host of health impacts, ranging from catastrophic direct effects (e.g., the recent cholera epidemic in Latin America and the chemical poisoning outbreak in Bhopal, India), to chronic effects (e.g., in Minamata, Japan), to subtle, indirect, and even disputed effects (e.g., in Love Canal, USA). Table 1 summarizes some of the major notorious disasters in the last half century that have caused “environmental disease” outbreaks. There are undeniably countless other examples of environmental disease outbreaks, some of which are not easily detectable on the macrostatistical level. Meanwhile, over a billion people in the world lack access to safe drinking water (WHO 1992b) and over 600 million are exposed to ambient levels of sulphur dioxide that well exceed recommended levels. Moreover the pressure on agriculture and food production as both population and per capita demand increase, will likely lead to a greater burden on the environment (see “Food and agriculture” in this chapter). Environmental health impacts thus include the indirect effects of industrial disruption of adequate food and housing, as well as the degradation of the global systems on which the health of the planet depends.

Table 1. Selected major "environmental disease" outbreaks

In many countries large-scale agriculture and the concomitant active use of toxic pesticides is a major health hazard both for workers and for their households. Pollution by fertilizers or biological waste from the food industry, paper industry and so on can also have harmful effects on waterways, reducing fishing and food supplies. The fishermen and gatherers of other seafood may have to travel much further to get their daily catch, with increased risks of drowning accidents and other mishaps. The spread of tropical disease by the environmental changes associated with developments such as the building of dams, roads and so on constitutes another type of environmental health risk. The new dam may create breeding grounds for schistosomiasis, a debilitating disease affecting rice farmers who have to walk in water. The new road may create fast communication between an area with endemic malaria and another area hitherto spared from this disease.

It should be pointed out that the major basis for a harmful environment in the workplace or in the general environment is poverty. The traditional health threats in developing countries or in poor sections of any country include poor sanitation, water and food which spreads communicable diseases, poor housing with high exposures to cooking smoke and high fire risks, as well as high injury risks in small-scale agriculture or cottage industries. Reduction of poverty and improved living and working conditions is a fundamental priority for improved occupational and environmental health for billions of people. Despite efforts for energy conservation and sustainable development, failure to address the underlying inequities in wealth distribution threatens the global ecosystem.

Forests, for example, which represent the culmination of ecological successional processes, are being destroyed at an alarming rate, due to commercial logging and clearance by impoverished peoples for agriculture and firewood. The effects of forest depletion include soil erosion, which, if extreme, can lead to desertification. Loss of biodiversity is an important consequence (see “Species extinction, biodiversity loss and human health” in this chapter). It is estimated that one-third of all carbon dioxide emissions are from the burning of tropical forests (the importance of carbon dioxide in creating global warming is discussed in “Global climate change and ozone depletion” in this chapter). Thus, addressing poverty is imperative with respect to global environmental health as well as individual, community and regional well-being.

Reasons for Linking Environmental and Occupational Health

The main link between the workplace and the general environment is that the source of the hazard is usually the same, whether it is an agricultural activity or an industrial activity. In order to control the health hazard, a common approach may work effectively in both settings. This is particularly so when it comes to the choice of chemical technologies for production. If an acceptable result or product can be produced with a less toxic chemical, the choice of such a chemical can reduce or even eliminate the health risk. One example is the use of safer water-based paints instead of paints made with toxic organic solvents. Another example is the choice of non-chemical pest-control methods whenever this is possible. In fact, in many cases, particularly in the developing world, there is no separation between the home and the workplace; thus the setting is truly the same.

It is now well recognized that the scientific knowledge and training required to assess and control environmental health hazards are, for the most part, the same skills and knowledge required to address health hazards within the workplace. Toxicology, epidemiology, occupational hygiene, ergonomics, safety engineering - in fact, the very disciplines included in this Encyclopaedia - are the basic tools of environmental science. The process of risk assessment and risk management is also the same: identify the hazards, categorize the risks, assess the exposure and estimate risk. This is followed by evaluating control options, controlling the exposure, communicating the risk to the public and establishing an on-going exposure- and risk-monitoring programme. Thus occupational and environmental health are strongly linked by common methodologies, particularly in health assessment and exposure control.

The identification of environmental health hazards has often come from observations of adverse health outcomes among workers; and unquestionably it is in the workplace that the impact of industrial exposures is best understood. Documentation of health effects generally comes from one of three sources: animal or other laboratory experiments (both non-human and controlled human), accidental high-level exposures or the epidemiological studies that usually follow such exposures. To conduct an epidemiological study it is necessary to be able to define both the exposed population and the nature and level of the exposure, as well as to ascertain the negative health effect. It is generally easier to define the members of a workforce than to determine the membership of a community, particularly in a community that is transient; the nature and level of exposure to various members of the cohort are generally more clear-cut in a workplace population than in a community; and the outcomes of high levels of exposure are almost always easier to delineate than more subtle changes attributable to low-level exposure. While there are some examples of exposure outside factory gates approaching the worst occupational exposures (e.g., cadmium exposure from mining in China and Japan; lead and cadmium emissions from smelters in Upper Silesia, Poland), the levels of exposure are generally much higher to a workforce than to the surrounding community (WHO 1992b).

Since adverse health outcomes are more apparent in workers, information on occupational health effects of many toxic exposures (including heavy metals such as lead, mercury, arsenic and nickel, as well as such well-known carcinogens as asbestos) has been used to calculate the health risk to the wider community. With respect to cadmium, for example, as early as 1942 reports began to appear of cases of osteomalacia with multiple fractures among workers in a French factory producing alkaline batteries. During the 1950s and 1960s cadmium intoxication was considered to be strictly an occupational disease. However, the knowledge gained from the workplace helped achieve the recognition that osteomalacia and kidney disease that was occurring in Japan at this time, “Itai-itai” disease, was indeed due to contamination of rice from irrigation of soil with water contaminated with cadmium from industrial sources (Kjellström 1986). Thus occupational epidemiology has been able to make a substantive contribution to knowledge of the effects of environmental exposure, constituting another reason for linking the two fields.

On an individual level, occupational disease affects well-being in the home and the community; and, universally, an individual who is ill from inadequacies in the home and the community cannot be productive in the workplace.

Strictly from a scientific viewpoint, there is a need to consider total (environmental plus occupational) exposures in order to truly assess health impact and establish dose-response relationships. Pesticide exposure is a classic example wherein occupational exposure may be supplemented by considerable environmental exposure, through food and water-source contamination, and through non-occupational airborne exposure. From outbreaks in which over 100 poisonings occurred from contaminated food alone, over 15,000 cases and 1,500 deaths due to pesticide poisoning have been documented by the WHO (1990e). In one study of Central American cotton growers using pesticides, not only did very few of the workers have access to protective clothing, but virtually all of the workers lived within 100 metres of the cotton fields, many in temporary housing with no walls for protection from aerial pesticide spraying. The workers also often washed in irrigation channels containing pesticide residues, resulting in increased exposures (Michaels, Barrera and Gacharna 1985). To understand the relationship between pesticide exposure and any health effects reported, all sources of exposure should be taken into consideration. Thus ensuring that occupational and environmental exposures are evaluated together improves the accuracy of exposure assessment in both areas.

The health problems caused by occupational and environmental hazards are particularly acute in developing countries, where well established methods of hazard control are less likely to be applied because of limited awareness of the hazards, low political priority of health and environment matters, limited resources or lack of appropriate occupational and environmental health management systems. A major impediment to environmental health hazard control in many parts of the world is the lack of people with appropriate training. It has been documented that developing countries suffer from a severe shortage of expert staff in occupational health (Noweir 1986). In 1985 a WHO expert committee also concluded that there is an urgent need for staff trained in environmental health matters; indeed Agenda 21, the internationally agreed upon strategy taken by the United Nations Conference on Environment and Development (UN 1993), identifies training (national “capacity building”) as a key element of promoting human health through sustainable development. Where resources are limited, it is not feasible to train one group of people to look after health concerns within the workplace, and another group to attend to hazards outside the factory gate.

Even in developed countries, there is a strong trend to make most efficient use of resources by training and employing “occupational and environmental health” professionals. Today, businesses must find ways to manage their affairs logically and efficiently within the societal framework of duty, law and financial policy. Combining occupational and environment health under one roof is one way of achieving this goal.

Broad environmental concerns must be taken into consideration in designing workplaces and deciding on industrial hygiene control strategies. Substituting for one substance another one that is less acutely toxic may make good occupational health sense; however, if the new substance is not biodegradable, or damages the ozone layer, it would not be an appropriate exposure control solution—it would only move the problem elsewhere. The use of chlorofluorocarbons, now widely used as a refrigerant instead of the more acutely dangerous substance ammonia, is the classic example of what is now known to have been an environmentally inappropriate substitution. Thus linking occupational and environmental health minimizes unwise exposure control decisions.

While understanding of the health effects of various deleterious exposures has usually come from the workplace, the public health impact of environmental exposures to these same agents has often been a major force in stimulating clean-up efforts both inside the workplace and in the surrounding community. For example, discovery of high lead levels in workers’ blood by an industrial hygienist in a lead foundry in Bahia, Brazil, led to investigations of lead in the blood of children in nearby residential areas. The finding that the children had high lead levels was a major impetus in the company taking action to reduce occupational exposures as well as lead emissions from the factory (Nogueira 1987), although occupational exposures still remain substantially higher than would be tolerated by the general community.

In fact, environmental health standards are usually much stricter than occupational health standards. The WHO’s recommended guideline values for selected chemicals provide an example. The rationale for the difference is generally that the community consists of sensitive populations including the very old, the ill, young children and pregnant women, whereas the workforce is at least healthy enough to work. Also, it is often argued that risk is more “acceptable” to a workforce, as these people are benefiting by having a job, and are therefore more willing to accept the risk. Many political, ethical, as well as scientific, debates rage around the question of standards. Linking occupational and environmental health can be a positive contribution to sorting out these controversies. In this regard, tightening the connection between occupational and environmental health may facilitate greater consistency in approaches to standard setting.

Likely inspired at least in part by the active debate about the environment and sustainable development brought to the forefront by Agenda 21, many occupational health professional organizations have changed their names to “occupational and environmental” organizations in acknowledgement that their members are increasingly devoting their attention to environmental health hazards both inside and outside the workplace. Further, as noted in the chapter on ethics , the International Code of Ethics for Occupational Health Professionals states that the duty to protect the environment is part and parcel of the ethical obligations of occupational health professionals.

In summary, occupational and environmental health are strongly linked by:

• the very fact that the source of the health threat is usually the same

• common methodologies, particularly in health assessment and exposure control

• the contribution that occupational epidemiology makes to knowledge of the effects of environmental exposure

• the effects that occupational disease has on well-being in the home and the community, and conversely the effect of environmental pathology on worker productivity

• the scientific need to consider total exposures in order to determine dose-response relationships

• the efficiency in human resource development and utilization gained by such a linkage

• improvements in exposure control decisions stemming from the broader view

• greater consistency in standard setting facilitated by the link

• the fact that linking environmental and occupational health enhances the incentive for rectification of hazards to both the workforce and the community.

The desirability of bringing together occupational and environmental health notwithstanding, each has a unique and specific orientation that should not be lost. Occupational health must continue to focus on workers’ health, and environmental health must continue to concern itself with the health of the general public. None the less, even where it is desirable for professionals to operate strictly in only one of these fields, having a good appreciation of the other enhances the credibility, knowledge base and effectiveness of the overall endeavour. It is in this spirit that this chapter is presented.

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