The paper elaborates the utilization of a novel 6 × 6 Occupational Health Hazard Risk Rating matrix developed for oil and gas operations,enhancing the determination of occupational health hazards as comparedto a5 × 5 matrix in terms of clarity on severity and likelihood criteria. This paper describes how severity ratings were redefined, and how likelihood ratings were divided into qualitative and quantitative approaches.

To establish the severity rating definitions, health effect ratings were benchmarked from international industrial hygiene association guidelines, peer-reviewed literature, and hazard rating categories from oil and gas operations. The qualitative likelihood scheme was developed considering evaluation methodologies for various physical and ergonomic hazards, as well as formulation of control bands for biological and chemical hazards. The quantitative likelihood scheme was based on the concept of the 95% upper UCL of hazard exposure data and evaluating it against its OEL.

From the previous five (5) Severity of Harm categories (i.e., Minimal, Minor, Moderate, Major, Extreme), six (6) classifications were developed (i.e., Notable, Minor, Serious, Major, Catastrophic, Disastrous) specifying documented health effects posed by a workplace health hazard. From the previous five (5) Likelihood of Harm categories (i.e., Rare, Unlikely, Possible, Likely, Almost Certain), six (6) qualitative likelihood classifications were formulated (i.e., Very Low, Low, Medium/Moderate, Moderately High, High, Very High) considering current evaluation schemes for physical and ergonomic hazards and control banding for biological and chemical hazards. In addition, six (6) exposure bands were created by defining specific exposure rating categories based on an estimate of the 95% UCL relative to a health hazard’s OEL. Finally, the previous five (5) risk ratings (i.e., Extreme, High, Medium, Low, Negligible) were consolidated into four (4) risk levels (i.e., High, High-Medium, Medium and Low), with each level differentiated according to the control measures required and the exposure monitoring frequency requirement for the workplace health hazard.

The health hazard risk rating matrix is envisioned to make health hazard risk assessment process simple, more accurate, user-friendly, and consistent with international best practices for the following reasons: use of 95% UCL is the most appropriate metric to evaluate exposures on the upper tail of an exposure distribution as it acts as a reference point in assessing the exposure profile’s arithmetic mean with a health hazard’s OEL; new severity rating definitions mirror the actual health effects posed by a health hazard; and qualitative likelihood rating is reflective of globally accepted exposure assessment methodologies and control banding schemes.

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