This diagram, derived from Ramachandran and co-authors,
illustrates the American Industrial Hygiene Association, or AIHA, "Exposure Assessment Strategy"
that can be used by occupational health and safety specialists.
An organization must decide to establish an exposure assessment strategy at the start.
This is the "anticipate" part of the occupational hygiene framework.
Next comes basic characterization of the workplace, the work force, and the agents that may be present in the workplace.
This is the "recognize" part of the occupational hygiene framework.
Next is exposure assessment.
This involves defining similar exposure groups, establishing exposure profiles,
and making judgments about the acceptability of exposures.
This is the evaluate portion of the occupational hygiene framework.
Further actions vary depending on the specialist's judgment of an exposure's acceptability.
If an exposure's acceptability is uncertain, additional information must be gathered to better assess the exposure.
If an exposure is unacceptable, it needs to be controlled in some manner to reduce the exposure.
This is the control part of the occupational hygiene framework.
If an exposure is acceptable, then it is reassessed regularly to ensure that it remains acceptable.
This means that exposure assessment is a cyclical endeavor.
Based on the exposure acceptability judgment, action is taken, but then exposure must be continually reassessed.
Digging in a little deeper, the first step, as described by Mulhausen and Damiano,
is for a work organization to start by establishing an exposure assessment strategy.
The specific roles of occupational hygienists, other specialists, management,
and workers in the exposure assessment process should be addressed.
In addition, the organization must decide on its exposure assessment goals,
in particular whether the organization is interested primarily in complying with government regulations
or if it seeks to protect workers comprehensively at all times,
which may require greater investment of time and money than merely complying with regulations.
The organization's exposure assessment program should be written down and shared with all stakeholders.
This document should indicate the specific methods and criteria that the organization will use.
The next step, basic characterization, involves gathering information about the workplace, the work force,
and the agents that may be present in the work environment.
When characterizing the workplace, an occupational hygienist will ask, "What are the environmental conditions in the workplace?
Is it indoors or outdoors? What are the temperature and relative humidity in the workplace?"
The hygienist will also seek to understand the processes and operations in the workplace,
and whether control measures are already present.
When characterizing a work force, an occupational hygienist must understand the structure of the work force:
for example, what does the organizational chart look like,
how are departments organized, and how many work shifts does the organization use?
Hygienists should also identify job categories and classifications, find out the numbers of workers in each job, and delineate work tasks.
To characterize agents in a workplace, a hygienist will ascertain the quantities of materials used and the chemical, physical, and
biological properties of those materials. In addition, the occupational exposure limits will be identified for the materials that are present.
Performing an initial exposure assessment is the third step.
As part of the exposure assessment process, occupational hygienists define similar exposure groups, or SEGs.
SEGs are groups of workers who have the same general exposure to the agent being assessed
due to similarities in the tasks they perform, the materials and processes with which they work, and the ways they carry out the tasks.
An exposure profile is a characterization of exposure levels for an SEG.
A central tendency for the exposure must be estimated as well as the day-to-day variability of the exposure.
While optimal for calculating values such as means, medians, geometric means, standard deviations, geometric standard deviations,
and confidence limits, quantitative exposure concentration data are often unavailable or limited initially.
If this is the case, a qualitative assessment about exposure levels and variability may be necessary,
drawing on an occupational hygienist's knowledge, experience, and professional judgment.
Using these quantitative or qualitative assessments,
occupational hygienists make judgments regarding exposure acceptability.
Exposures are rated as acceptable or unacceptable, or the acceptability may be deemed uncertain.
This is done by comparing exposures to occupational exposure limits.
If the exposure acceptability is uncertain, the occupational hygienist must gather more information.
This may be accomplished by making more measurements to monitor exposures,
estimating exposures using predictive models, and/or performing biological monitoring to measure internal doses.
More detailed information may be gathered by performing toxicological studies using animals or epidemiological studies
with data collected from groups of workers to compare exposures to adverse health outcomes.
More information gathering helps hygienists to make a better judgment of the acceptability of exposures by having better data.
If exposures are clearly unacceptable for an SEG, then controls should be implemented to manage the risk of exposure.
This is accomplished by utilizing the hierarchy of controls:
elimination, substitution, engineering controls, administrative controls, and personal protective equipment.
After they are implemented, the effectiveness of the controls should be assessed.
Once exposures reach a level that is considered acceptable, they should be continually reassessed.
Information about the workplace should be kept up-to-date.
Have the similar exposure groups changed at all? Have work tasks changed due to changes in the organization of work?
Have new processes been put in place? Have occupational exposure limits changed to an extent
that an exposure previously rated as acceptable may now be unacceptable or have an uncertain acceptability?
The bottom line is that exposure assessment is never quote-unquote done.
Lastly, communication and documentation are important.
Exposure assessment findings must be communicated to the workers, who are most affected by the exposures.
They must also be communicated to supervisors and managers,
and to the entire occupational health and safety staff of the organization.
Documentation of procedures for exposure assessment is important,
as is retaining records of the results of assessments.
Hazard control plans that are put in place should also be documented.
In summary, the exposure assessment strategy established by the American Industrial Hygiene Association
includes starting by establishing a strategy within a work organization,
followed by basic characterization of the workplace and an initial exposure assessment that leads to a judgment of the acceptability
or unacceptability of an exposure.
Then, based on that judgment, a plan is established to either gather more information,
implement health hazard controls, or reassess the exposure periodically.
Making sure to communicate and document the procedures and results of the exposure assessment
is also an important element of the strategy.
This is a cyclical process. So, exposure assessment is never really complete in a workplace.