The key is to select a model that is simple enough to use but can provide a relevant answer to support an appropriate decision.
AIHA’s launch of the Product Stewardship Society in 2012 was in part an acknowledgement of the industrial hygienist’s core skills relating to exposure and risk assessments (EA/RA), not only for primary production workers but for a broader range of potentially exposed populations, including downstream industrial and commercial workers, consumers, and the general population. These exposures stem from uses of products and subsequent releases to air, water, soil, wildlife, and food production. This article introduces some of the tools industrial hygienists can bring to EA/RA for downstream product use.

MANUFACTURING VS. DOWNSTREAM USE Exposure assessments for both manufacturing and product use begin by looking at the tasks workers or users perform that put them in potential contact with the hazard. This evaluation may require an understanding of the physical and chemical properties of the hazard; the nature and severity of its toxicity; and the frequency, duration, and intensity of the contact, possibly by all relevant exposure routes, as well as the environmental conditions (temperature, ventilation, control technologies) during use. The exposure evaluation could include professional judgment, exposure/control banding, screening measurements, more detailed measurements, or mathematical modeling. The results might be compared qualitatively or quantitatively to an occupational exposure limit.
For occupational exposures, our goal is typically to determine if they are acceptable as a ceiling limit, a short-term exposure limit (STEL), or a time-weighted average (TWA) for an adult worker throughout a full working career. But exposures for consumers and the general population aren’t limited to a working day. They are assessed over various times—a short-term application, a 24-hour period, or an entire lifetime.
Exposure assessments for manufacturing environments differ in several ways from those for downstream users of consumer products. At the start, the relevant populations are characterized through scenarios describing the product’s properties; the quantity, frequency, and duration of its use; and the environmental conditions. In occupational settings, we consider many types of hazardous endpoints, including CMT (carcinogen, mutagen, and teratogen) exposures and risks. These may be of even greater concern in general population and consumer applications. Efficacy of exposure controls in downstream and consumer uses can be quite different than in primary production operations. Controls against inhalation, ingestion, and dermal uptake are often difficult to ensure for consumers because we can’t assume they’ve received training and education on the hazards or that they’ll use the proper PPE.
Concerns about sensitive sub-populations are more extensive with consumers. Sub-populations include adults in childbearing years and children with in-residence exposure for nearly 24 hours a day. Children have much different activity patterns than workers or general population adults; for example, infants crawl on floors and carpets and exhibit frequent hand-to-mouth behavior. Oral exposure is less frequently an occupational exposure concern.
For assessments of consumers and the general population, the exposure assessor must understand which population segments are potentially most at risk and their “exposure factors” such as body weight, breathing rate, hand-to-mouth behavior, and dermal contact/uptake, as well as the composition, frequency, duration, and intensity of the exposure. The allowable exposure guidelines, which include but are not limited to an Acceptable Daily Dose (ADD) and Allowable Daily Intake (ADI), must then reflect the possibly unique characteristics of the at-risk populations.
Editor’s note: This is the third article in a four-part series on mathematical modeling in exposure assessment, following “Patterns of Exposure” by Chris Keil (January 2017) and “Easy Modeling” by Paul Hewett (April 2017). The final article, to be published in December, will discuss models for emergency response planning.
Considerations for Exposure Assessment of Consumer Products
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