Do OELs Really Protect Workers from Reproductive and Developmental Effects?
The latest data from the United States Census Bureau indicate that 66 percent of women who gave birth to their first child between 2006 and 2008 worked during their pregnancy. That figure is a dramatic increase from earlier generations; for example, only 44 percent of women who had their first child during the 1960s worked during pregnancy. Given this trend, the potential impact of workplace chemical exposures on reproduction and development is a significant concern. This concern involves not only exposures of pregnant women but also of male and female workers prior to conception. Furthermore, because children may be exposed to chemicals via breast milk, the period of concern for developmental toxicity does not cease at birth. Here we address the question of whether occupational exposure limits (OELs) protect workers against developmental and reproductive toxicity (DART) effects. We also identify several difficulties that industrial hygienists may face in assessing the appropriateness of an OEL for workers who are pregnant or who expect to conceive. OELS AND DART EFFECTS The basic process for developing an OEL, as described in a December 2015 supplement to the Journal of Occupational and Environmental Hygiene (JOEH), is to review and evaluate relevant scientific literature; select the critical health endpoint (that is, the most sensitive effect); select the point-of-departure (POD) from the key study (the dose or concentration near the low end of the observed range of the critical health endpoint); apply assessment factors that most appropriately represent the uncertainty and variability associated with the POD; and calculate the OEL as the POD divided by the assessment factors. (The calculation may involve other factors such as route-to-route extrapolation, animal-to-human conversions, or other adjustments.) Although definitions vary slightly, the resulting OEL is generally intended to protect all or the vast majority of workers against adverse effects during their working lifetime and beyond.
Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers