Occupational health impacts: offshore crane lifts in life cycle assessment

The identification and assessment of environmental tradeoffs is a strongpoint of life cycle assessment (LCA). A tradeoff made in many product systems is the exchange of potential for occupational accidents with the additional use of energy and materials. Net benefits of safety measures with respect to human health are best illustrated if the consequences avoided and health impacts induced by additional emissions are assessed using commensurable metrics. Our aim is to develop a human health impact indicator for offshore crane lifts. Crane lifts are a major cause of accidents on offshore oil and gas (O & G) rigs, and health impacts from crane lift accidents should be included in comparative LCA of O & G technologies if the alternatives differ in the use of crane lifts.

Accident records for mobile offshore petroleum installations were used to develop an empirical occupational health indicator for crane lifts in LCA. Probabilistic parameters were introduced in the procedure, and results were calculated by Monte Carlo simulation. The disability adjusted life years (DALY) framework was used to classify health outcome. The characterization factor for offshore crane lifts was applied in three comparisons to evaluate the significance of crane lifts to human health impacts from drilling technology.

The mean occupational health impact per crane lift was 4.5∙10⁻⁶ DALY, with cumulative percentiles {P _2.5, P ₅₀, P _97.5} = {6.0∙10⁻⁷, 3.1∙10⁻⁶, 1.7∙10⁻⁵}. Analogously, the fatal accident frequency was described by {P _2.5, P ₅₀, P _97.5} = {7.6∙10⁻⁹, 3.9∙10⁻⁸, 2.0∙10⁻⁷}, with mean 5.6∙10⁻⁸ lives lost per crane lift.

The uncertainty in the results is caused mainly by the random nature of accidents, i.e., variability in accident frequency. Applications of the characterization factor indicate that although crane lifts may not be significant to the overall health impact of the life cycle of drilling fluids, they are important to the occupational safety of employees on offshore drilling rigs and contribute significantly to the life cycle health impact of loading technologies used to transport drilling waste to shore. A comparative LCA of technologies for loading and off-loading drilling wastes shows that a recently developed hydraulic system performs better than the traditional crane lift alternative in terms of human health impacts.

With the availability of statistics to assess the risk of single mechanical operations, safety aspects may well be included in LCA. For the case of offshore crane lifts, the uncertainty in the characterization factor compares favorably to what is indicated for other human health impact chains. In further work of quantifying occupational health impacts in DALY using accident statistics, it is advised to see if records of non-recoverable injuries (fatalities and amputation cases) can be used to simplify the damage assessment procedure as recoverable injuries were insignificant to the total burden from crane accidents.

The characterization factor for crane lifts identifies contributions to life cycle health impact from loading technologies that otherwise would have been overlooked in LCA. While many contest the inclusion of occupational accidents in LCA, our results show that such impacts can be included and that their consideration adds valuable insights.