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Phases in the evaluation of the occupational exposure to chemical substance/API. Phase 3: Quantitative evaluation of the risk of inhalation.

Evaluation Chemical Substance

After the banding control has been established along with the strategies to be followed, it is necessary to carry out a control of the exposure and establish corrective measures (depending on the “Risk Factors” and their priority). A quantitative evaluation of the exposure must be done to check the corrective measures. To this end, we have to determine the exposure by doing calculations using the result of the exposure measurements and times to find the degree of exposure at which health is affected.

The new draft of the European standard UNE 689 (7) concerning the assessment of the risk of inhalation of chemical substances in the work place which will come into force early in 2018 establishes a strategy to do the representative measurements concerning inhalation exposure of chemical agents to be able to demonstrate compliance in relation to the OEL value level. This new draft applies to threshold values with reference periods lasting for 15 minutes or over.

The new draft of the UNE 689 (7) standard offers the possibility of concluding (exceeding or not the threshold value) based on a Basic Characterisation. Basic characterisation focuses on three aspects:

The chemical agent has been identified in Phase 1 and the factors reviewed in Phase 2, consequently, we must now estimate exposure.

Exposure estimate

The first measurement strategy is based on the constitution of the Similar Exposure Groups (SEGs) with the same general exposure profile for the chemical agent(s) based on similarity and the frequency of the tasks performed, the materials and the processes with which they are used and the similarity of the way in which the tasks are conducted. A SEG can cover workers in different places.

Based on a few representative exposure measurements obtained by some workers included in the SEG, if the results indicate that the OEL value is met, this can be extrapolated to all SEG workers.

The measurement procedure will take the following into account:

  • Sampling and analysis techniques in accordance with the standards (EN482)
  • Personal sampling will be used (breathing area)
  • The duration of the sampling must be representative of the limit reference period: OEL-8 hour TWA or OEL-15 min (STEL), at least two (2) hours to establish the exposure situations.
  • The measurements must be done on a sufficient number of days and during several specific operations (variability)
  • The minimum number of measurements depends on the statistics used to check compliance with the OEL value (3-6 measurements)
  • The number of workers in the SEG will be taken into account to determine the number of measurements
  • The technician must remain on site to supervise the success of the sampling operation and collect all the information to interpret or validate the results

If it has not been possible to conclude on the basis of the Basic Characterisation, 3 – 5 samples will be needed (≥ 2 h) which are considered as representative (separated in time and space) to do the screening test:

  • 3 samples: < 0.1 OEL
  • 4 samples: < 0.15 OEL
  • 5 samples: < 0.2 OEL

OEL non-compliance occurs if one of the samples is > OEL

We at Azierta have an expert toxicology team (AETOX, EUROTOX and ERT accredited) in determining occupational exposure limits and in APIs Categorization, which associates the exposure limits with specific safety measures (engineering control, standardised work processes and safety equipment). Our multi-disciplineOccupational Health and Safetyteam has the expertise, moreover, to design complete health vigilance protocols to ensure safe work environments.

If you wish to learn more about this aspect of our work, visit Azierta: OEL and API Categorisation and follow us on our social networks


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