10.1. Introduction

 

The impact of stressors on health is characterised by several causes with different strengths of association. This means that the links between exposures and their health consequences depend on the environmental pollutants and diseases being considered, but are also influenced by factors such as genetic constitution, age, nutrition and lifestyle, and socioeconomic factors such as poverty and level of education (EEA, 2005). Important elements of exposure and risk assessment are estimations of the body burden of chemicals, combined exposures from multiple sources (food, air and water), the 'cocktail-effect' and the timing of exposures. The topic of 'Late responses to early exposure' needs to be addressed, taking account individual and generational exposure and their effect. Preventive measures require the development of a proactive risk assessment and management responses that can contribute to the formulation of suitable measures, taking into account complexities and uncertainties.

 

The structure and condition of health determinants affect the level and sustainability of the population’s health. An up to date understanding of the health determinants and their interactions is critically important for public health research and practice (Beaglehole, 2004). Genetic factors, individual physical and psychological resources as well as coping skills, and the social, cultural, occupational, political, economic and health care environment interact in the determination of the health status of individuals and of the community. Biochemical / somatic, psychological / emotional, and social (public or private) interchanges and interactions are not only critical with regard to disease factors, but also for what concerns well-being and human development. All factors are more or less dynamic rather than fixed elements of human experience which determine the chance of morbidity and mortality (Hart, 2004). The focus on single determinants or single groups of determinants alone is most likely insufficient to improve the health status. This is particularly important for health policy interventions. Associations between determinants are not static, but vary significantly across the lifespan. The impact of environmental determinants is more significant on the health of vulnerable subpopulations such as the elderly and children (Beaglehole, 2004; Meusel et al, 2005; Meusel et al, 2006).

 

Determinants of risk behaviours are complex and interwoven with socio-economic, cultural, and psychosocial determinants / factors (Green and Potvin, 2004). It is most important to acknowledge these interrelationships and address them in analysis. Due to the high complexity of associations and interactions of health determinants, however, statistical modelling only allows the analysis of simplified scenarios involving selected determinants and their interrelationship (Szklo and Nieto, 2005). In general, healthy and unhealthy lifestyle factors tend to cluster. People who engage in regular physical activity are more likely to follow current dietary recommendations and less likely to smoke (Parsons et al, 1999).

 

The model in Figure 10.1.1 illustrates the different factors that influence health, from those at individual level to those of societal and cultural nature (Dahlgren and Whitehead, 1991).

 

Figure 10.1.1. The model of health determinants

 

 

 

 

A similar message is also conveyed by Figure 10.1.2 and, together with Table 10.1.1, by Figure 10.1.3.

 

 

 

 

 

 

 

Figure 10.1.3. The interaction between health determinants and human beings

 

 

Table 10.1.1. Health determinants:  agents, exposure routes, human settlements and settings, human individual characteristics and social factors influencing health

 

AGENTS	EXPOSURE ROUTES	LIVING AND WORKING ENVIRONMENT	HUMAN    INDIVIDUAL CHARACTERISTICS
Physical	Inhalation and air pollution	Housing	Genetic Factors
Chemical	Ingestion of contaminated food and drinking water	Schools	Developmental Factors
Biological	Contact with non food consumer products	Urban, Rural and Industrial	Age
Climatic Changes and extreme weather conditions	Multiple exposures	Leisure areas	Lifestyles
		Workplace	Physiological risk indicators
		Transport
		Social networks and social environment
		Socio-economic inequalities
		Violence and other behaviour against society

   

 

 

 

Individual health status can be regarded as depending on a variety of internal (endogenous) and external (exogenous) determinants. Basically five groups of determinants can be distinguished, as indicated here below: 1) endogenous attributes, either part of the individual genetic make-up or acquired during life; 2) personal behaviour (or lifestyle); 3) the conditions of the social environment, where the individual interacts with his peers, being influenced by the community; 4) the conditions of the living and working environment where the individual lives, works and finds access to essential services; 5) overarching determinants are the general economic, cultural and environmental conditions which shape the society, such as economic and labour market conditions and the role of women in the society.

 

Figure 10.1.2 shows another model of some of the most important health determinants. Environmental and external factors contributing to the health of individuals and populations include cultural, societal, and economic factors, as well as the physical environment and health care system. Individual health determinants such as genetic, physical, psychological and cognitive factors, may be in the causal pathway between these external health determinants and a particular outcome of interest, and act as confounders or effect modifiers (Figure 10.1.2) (Rosner, 2000; Szklo, 2000; Szklo and Nieto, 2005).

 

While constitutional characteristics are largely fixed, the other conditions might be modified by policies. Looking at public health and potential diseases with the ambition to assess the environmental contribution means consideration of multi-causality and interaction in order to identify causal factors, compare them and if possible quantify their contribution to a disease or to public ill-health, all in order to take preventive measures. A better understanding of the disease impacts of various exogenous factors can help guide policymakers in designing preventive health measures that not only reduce disease, but also reduce costs to the health-care system.

 

The physical environment includes most of the environmental exposures, physical factors such as radiation, noise, magnetic fields, suspended particles (including fibres), cold and heat, chemical factors such as hazardous substances in the outdoor and indoor environment, including the working environment, ambient air and food; and biological factors, such as the myriad of bacteria, viruses, and other micro-organisms, pollen or allergens of biological origin. 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. Of the 102 major diseases, disease groupings and injuries covered by the World Health Report in 2004, environmental risk factors contributed to the disease burden in 85 categories. Globally, an estimated 24% of the disease burden (healthy life years lost) and an estimated 23% of all deaths (premature mortality) was due to environmental factors (Ezzati et al, 2002). Potentially sensitive groups at higher risk for damage or disease from environmental pollutants are children, people with existing health problems such as diabetes, respiratory disease or heart disease and people with compromised immune systems, including those who have HIV/AIDS or are undergoing cancer chemotherapy. Poor or other disadvantaged populations who may live in more polluted environments are exposed to higher concentrations of pollutants. Children living in particularly adverse conditions, such as poor and abandoned children, street children and those who are exploited or are at high risk of injuries due to environmental factors. Moreover, certain populations who live in increasingly agricultural regions, for example, agricultural workers and their families are especially vulnerable to poisoning from pesticides. A fetus can be exposed in uterus when their mothers use pesticides, work in sprayed fields, or work near spraying operations.

 

Today there is widespread public concern about health impacts and their associations with environmental exposures. The strengths of such associations vary for different diseases/exposures – from a very likely association in the case of cancer/radon to a low likelihood as in the case of cancer/EMF.

 

Table 10.1.2. Major health impacts and some associations with environmental exposures to chemicals and other environmental stressors and lifestyle factors.

Source: European Environment Agency & Joint Research Centre  (2006).

 

Health impact	Associations with some environmental exposures
Infectious diseases	water, air and food contamination climate change-related changes in pathogen life cycle
Cancer	air pollution (PM), mainly PM2.5  or less smoking and environmental tobacco smoke (ETS) some pesticides asbestos natural toxins (aflatoxin) polycyclic aromatic hydrocarbons, e.g. in diesel fumes some metals e.g. arsenic, cadmium, chromium radiation (incl. sunlight) radon dioxins
Cardiovascular diseases	air pollution (carbon monoxide, ozon, PM) smoking and ETS carbon monoxide lead noise inhalable particles food, e.g. high cholesterol stress
Respiratory diseases, including asthma	smoking and ETS sulphur dioxide nitrogen dioxide inhalable particles (PM2.5 and PM10) ground-level ozone fungal spores dust mites pollen pet hair, skin and excreta damp
Skin diseases	UV radiation Some metals e.g. nickel pentachlorophenol dioxins
Diabetes, obesity	food, e.g. high fat poor exercise
Reproductive dysfunctions	polychlorinated biphenyls (PCBs) DDT cadmium phthalates endocrine disruptors pharmaceuticals
Developmental (foetal and childhood) disorders	lead mercury smoking and ETS cadmium some pesticides endocrine disruptors
Nervous system disorders	lead PCBs methyl mercury manganese some solvents organophosphates
Immune response	UVB radiation Some pesticides
Increased chemical sensitivity	multiple chemical exposures at low doses

 

Note: many stressors, like POPs, dioxins, pesticides and heavy metals, are under strict regulatory control.