Overview
Genetic differences may make some workers more susceptible to the impact of occupational and environmental exposures
Such exposures might also be passed to future generations through changes to the DNA of the germ cell or through epigenetic changes, although there is at present little evidence to support this
Exposures at work can affect male fertility and, where the mother is exposed during pregnancy, the viability of the pregnancy and the health of the infant
Given our current state of knowledge, selection for employment using the results of genetic screening cannot be well justified on either ethical or practical grounds
The duty of the employer is to provide a workplace that is safe for all workers, including those with genetic susceptibilities and those contemplating pregnancy
All healthcare professionals concerned with the health of patients who have reached working age need to consider whether a specific pathology or set of symptoms is related to exposures at work. Given our new knowledge of the human genome it is reasonable to ask also whether genetic susceptibility might help to explain why one worker develops the disease while many others with the same exposure do not. The question of interest here is whether some workers are genetically less able than others to respond to chemical or other challenge at work. Such gene–environment interactions are particularly difficult to study as the effect will be seen only where exposure has occurred and will only be correctly attributed if pains are taken to explore and document the exposure history. Such knowledge of the environment—in addition to the genome—is essential if we are to fully understand the impact on workers’ health: the genome is not readily manipulated, but exposures can in principle be controlled and health effects prevented. With our current knowledge such genetic susceptibility to a specific exposure would very rarely be a reason for excluding a worker, but may lead to greater understanding of the mechanisms by which disease occurs, and suggest approaches to prevention or treatment.
There is also concern that occupational or environmental exposures may affect subsequent generations through changes to stem cells. By this means an infant born to such a parent may be at greater risk of disease even if exposure of the parent has ceased long before the child is conceived. Recently the picture has become even more complex with the emergence of environmental epigenetics—examining the effects that the environment can have on gene expression while leaving unchanged the structure of the DNA. There is troubling (though not conclusive) evidence that some epigenetic changes resulting from occupational or environmental exposures (for example methylation of the germ cell) may be heritable by future generations, thus linking the three topics of this chapter (work, genetics and reproduction).
In all these areas, genetic susceptibility, genetic alteration and reproductive health, exposures in the working population may be of particular concern as these tend to be higher than exposures in the general population—they occur in a sub-population in which a large proportion is of reproductive age and where exposures are preventable. Exposure standards designed to protect workers do not currently take account of genetic differences in susceptibility. Environmental exposures to the general public (including the very young and pregnant or nursing mothers), through contaminants in food, water and in the air we breathe, may also be suspected of affecting reproductive health. Pressing questions remain about whether such exposures may cause infertility, affect the outcome of pregnancy or influence the development of the infant in later life.
Work and Genetics
Why should those professionally involved in occupational health be concerned with the genetic make-up of people in the workforce or who seek to join it? First, there are those whose genetic inheritance, even in the absence of a specific occupational exposure, will lead to disease that will put at risk themselves, their fellow workers or the general public. For example, a worker genetically programmed to develop Huntington’s disease may, if employed as a driver of a high-speed train, put the public at risk in the early stages of the disease before a diagnosis can be made that permits redeployment or retirement on medical grounds. Second, there may be genetic conditions, for example sickle cell disease, where work environments (such as in deep sea diving) that can be tolerated by other workers may induce a crisis in a worker carrying this gene and, as a result, the worker and others put at peril. Third, it may be that a particular genetic variant (or polymorphism) or a combination of variants, carries a risk of ill health if a worker is exposed to a chemical that is detoxified by the enzyme produced by the gene. Where such a disease is a serious threat to quality of life or life itself, it may be tempting to consider introducing screening to monitor such workers and exclude them from exposure.
The arguments for and against such genetic screening are summarized in Box 17.1. It should be noted that other reasoning may apply in different societies. Where there is no universal healthcare, for example screening for genetic disease might reduce the employer’s overall healthcare bill although the temptation to do this, for example in the United States, may be tempered by ethical and legal considerations. In the United Kingdom there is currently little or no genetic screening for employment. Following the 1995 Statement of the Human Genetics Advisory Committee (Box 17.2), which suggested consensual evidence-based genetic screening, the Human Genetics Commission recommended in 2002 that any employer considering offering testing should inform the Commission and employers are now required to do so. The balance of opinion is that, with our current state of knowledge, such screening for genetic susceptibility is seldom, if ever, justified either from an ethical or practical standpoint.
| Arguments for | Arguments against: |
| 1 May identify predispositions to disease that would put others at risk in certain jobs (e.g. Huntington’s disease) | 1 Potential for unethical and illegal discrimination |
| 2 May identify those at increased risk from specific job demands or exposures (e.g. sickle cell and diving: PON1 polymorphisms and organophosphates) | 2 Risk of invasion of privacy if not confidential and consensual |
| 3 Allows individuals to make informed choices about where to work | 3 Failure of employers in their duty to provide a workplace safe for all |
| 4 May reduce healthcare costs of society as a whole | 4 Poor predictive value with current level of Knowledge |
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