HUMAN OCCUPATIONAL AND PERFORMANCE LIMITS UNDER STRESS - THE THERMAL ENVIRONMENT AS A PROTOTYPICAL EXAMPLE

The authors wish to challenge the contemporary stress limits for worke rs exposed to adverse thermal conditions. Further, they wish to challe nge the basis upon which all such occupational stress exposures are fo unded. It is their contention that task performance level should be th e primary criterion for exposure. Change in behavioural performance ef ficiency is the most sensitive reflection of human response to stress. Such responses are superior as indices of incipient damaging effects compared with the traditional measurement of physiological function. E fficient and error-free performance is the principal criterion of cont emporary work, especially in high-technology systems. Therefore, conti nuing exposure after work performance efficiency begins to fail, but b efore current physiological limits are reached, is inappropriate for b oth the safety and the productivity of the individual worker, their co lleagues, and the systems within which they operate. Behavioural perfo rmance assessment should therefore supercede physiological assessment as the primary exposure criterion, although physiological measures sti ll provide important supplementary information. A new description of s uch performance thresholds for heat stress is presented, together with its substantive theoretical foundation. Performance limits are of gro wing importance for prescriptions to all forms of occupational exposur e and are critical necessities for future statements concerning compre hensive protective safety standards.