Page 413 - Industrial Ventilation Design Guidebook

368 CHAPTER 6 TARGET LEVELS

the OELs represent levels of exposure that are perceived to be realistic and at-
tainable at the time they are established. Political and socioeconomic aspects
are combined with scientific considerations in order to avoid the imposition of
administrative, financial, and legal constraints that would hold back the devel-
opment of enterprises while maintaining the aim of ensuring the health of
workers.
'Toward this goal the EU defines two types of OELs:
• Binding limit value
» Indicative limit value
Binding occupational exposure limit values reflect feasibility factors re-
lated to social acceptability. When the results of environmental monitoring
have to be compared with OELs, factors that influence exposure and that en-
tail preventive policies are considered. For these values member states shall es-
tablish a corresponding national binding occupational exposure limit value
based on but not exceeding the community limit value. That is, a binding limit
means a minimum requirement.
An indicative limit value is a more common type of limit that reflects ex-
pert evaluation based on scientific data where it is possible to identify the
highest level of exposure along with the corresponding reference time period
for which one can have confidence that there will be no adverse effects on
health. For any chemical agent for which an indicative occupational exposure
limit value is established at the community level, member states shall establish
a national occupational exposure limit value, taking into account the commu-
nity limit value and determining its nature in accordance with national legisla-
tion and practice.
This approach may provide an opportunity for consolidating and simpli-
fying old legislation on chemicals and for bringing OEL setting up to date
with respect to social aspects, balancing the participation of all interested par-
ties (the scientific community, industry, unions, and governments) and there-
fore advancing the establishment process much more rapidly.

6.2.4 Assessment of Exposure to Chemical Agents
It is appropriate here to give a few ideas on the assessment of workplace expo-
sure to chemical agents, although specialized literature in this field should be
consulted for details.
Determination and assessment of the risks of hazardous chemical agents
requires knowledge of, among other things, the nature of the agents, the type
and duration of the exposure, the gravity of risk, and the criteria chosen for
the OEL. The purpose is to make quantitative measurements of the work envi-
ronment in order to compare the exposure with the limit value by means of an
independent scientific assessment using the best available scientific methodol-
ogy.
However, assessing occupational exposure to airborne contaminants in a
representative way is not an easy task and requires a good deal of professional
judgment and reliance on a good methodology. There are many issues to be re-
solved, such as