The increased mechanization and complexity of modern work processes has led to a variety of threats to human health. The result is considerable human suffering and economic losses both to the individual and his employer. In developing countries, where skilled labour is scarce, occupational health is of particular importance.
The working environment itself causes occupational disease and injuries, fatigue, unsatisfactory man/machine relationships and physiological stresses. Risks are greater among the migrant workers who have no vocational training or industrial experience and whose illiteracy and ignorance make it difficult to understand written or oral instructions. Exposure to typical high temperatures or to high humidity causes heat stress. Special problems may also arise in connection with work at high altitudes or in thick forests.
In the USA, the direct costs of injuries and illnesses cost $65 billion, and indirect costs, such as lost wages, $106 billion per year. Approximately 1.8 million workers per year develop injuries related to work, and a third of them miss work because of their problems. At least 100,000 workers die each year - and three or four times that number are disabled - as a result of occupational disease attributed to new chemicals, many untested for safety, being introduced into industrial products and processes. In 1992, occupational illnesses such as lung cancer and lead poisoning caused 60,300 deaths and 862,000 illnesses.
A 1993 survey found that nearly 1 in 5 US workers had job-related back pain for a week or more during the previous year, and 22% had trouble with their hands (including carpal tunnel syndrome).