Anthropogenic Pollutant Impacts On Human Health And Ecosystems

Published on 15 April 2009 in Food, health and wellbeing

Introduction

Increasingly we are realising that endocrine disrupting compounds (EDCs) may compromise health and wellbeing, even at very low environmental concentrations. EDCs comprise a wide range of chemical pollutants derived from industrial, domestic and agricultural activities. Their common feature is the capacity to interfere with normal hormone actions. This can induce adverse effects on multiple physiological systems (reproduction; immune, thyroid, neuroendocrine and cardiovascular function; obesogenic systems; bone structure) and also can be carcinogenic. Since they are ubiquitous in the environment, are not easily degraded and accumulate in human and animal tissues, the related problems are likely to be with us for years to come. Furthermore most EDCs have been synthesised only in the last 60 years. Because many of their actions are exerted subtly on developing organisms, but expressed in the adult, many of their potential effects on human health and wellbeing have been recognised only recently. Because all animal species are susceptible to EDC effects, animal populations and the sustainability of ecosystems on which humans depend are at risk.

Key Points

EDCs are frequently dismissed as unimportant because:

most individual chemicals are present in the environment at concentrations well below those known to induce biological effects,
effects are frequently subtle and not associated with visible reductions in health, productivity or wellbeing,
empirical studies of effects of single chemicals on adult organisms seldom result in major effects
individuals can be differentially affected by exposure and some show no apparent effects.

However, the results of our research indicate that very low concentrations of multiple EDCs, acting together, perturb multiple physiological systems in our animal model (sheep). Effects observed include:

altered reproductive function, offspring behaviour and adult bone structure. Furthermore, the greatest effects are exerted in the fetus although some of the effects were also expressed in these individuals when they were adults.
changes in organ structure and gene and protein expression and so are not necessarily associated with visible changes in health or reproductive performance. Nevertheless, they are consistent with recent reports that indicate long term reductions in human fertility and increasing incidences of certain cancers.

Research Undertaken

Through the application of sewage sludge to pastures, sheep have been exposed to environmental concentrations of a mixture of EDCs that are broadly associated with humans and their activities. A control, flock was grazed on pastures treated with inorganic fertiliser.

Sewage sludge is known to contain large amounts of many different EDCs but the application of sludge to pasture has been shown to result, only, in very small, often non-significant increases in soil concentrations of pollutants. Effects on tissue concentrations of individual EDCs of exposure to a mixture of pollutants, through sludge treatment of pastures, have also been found to be minimal. Nonetheless, exposure has been shown to be associated with significant disruption of:

fetal ovarian gene and protein expression,
fetal testicular structure, expression of various genes in the fetal brain that control reproduction and growth
structure of the adult sheep bones and mammary gland.

Preliminary studies also suggest perturbation of fetal thyroid and uterine function.

Policy Implications

The potential risks to human and animal health and wellbeing associated with exposure to EDCs is being increasingly recognised. However, EDCs are fundamentally important to our lifestyle and food production and are included, for example, in pesticides, herbicides and components of plastics, paints, adhesives and many other products. It is therefore logistically impossible to completely ban their production. The EU is already beginning to address regulation of EDC production and use through the Registration, Evaluation, Authorisation and restriction of CHemical substances (REACH )programme. This will help to identify the EDCs which are of greatest biological significance. However, the success of this programme will depend, ultimately, on understanding of the processes of environmental transport and degradation of EDCs, uptake by animals and humans and understanding of their mechanisms of action on a range of physiological systems. Our studies contribute to this understanding.

The results of our studies to date suggest that the:

a) investigation of the combined effects of low concentrations of multiple EDCs is essential to understanding the associated risks.

b) regulation of disposal or recycling of products containing these chemicals should be reviewed in the light of observed effects.

c) assessment of risk must address effects of exposure on fetal or early life stages of development.

Author

Dr Stewart Rhind, The Macaulay Land Use Research Institute s.rhind@macaulay.ac.uk

Topics

Food, health and wellbeing