Thyroid homeostasis in B6C3F1 mice upon sub-chronic exposure to trifluoroiodomethane (CF3I)

Trifluoroiodomethane (CF3I) is a fire suppressant gas with potential for use in low global-warming refrigerant blends. Data from studies in rats suggest that the most sensitive health effect of CF3I is thyroid hormone perturbation, but the rat is a particularly sensitive species for disruption of thyroid homeostasis. Mice appear to be less sensitive than rats but still a conservative model with respect to humans. The purpose of this study was to test tolerance and thyroid response to CF3I in B6C3F1 male mice. Male mice were exposed to CF3I for 6 h per day, for 28 days, via whole body exposure at concentrations of 2500, 5000 and 10,000 ppm. A 16-day recovery period was included to evaluate reversibility. No adverse clinical signs were observed throughout the study, and body weights were unaffected by exposure. CF3I exposure had no effect on thyroid histology. An increase in relative thyroid weight was observed at 10,000 ppm on day 28 but not in a separate group of animals evaluated on day 29, and thyroid weight was not different from controls at 44 days. Slight and sporadic changes in serum triiodothyronine, thyroxine, and thyroid-stimulating hormone were observed but did not follow a consistent pattern with respect to timing, dose, or direction. Overall, exposure at up to 10,000 ppm (1.0%) of CF3I gas for 28 days produced no overt general toxicity and only transient, recoverable effects on thyroid weight and hormones at certain concentrations. On the basis of the effect of CF3I exposure on the thyroid, including evaluation of thyroid histopathology, the no observed adverse effect level for this study is 10,000 ppm. Considering the apparently greater toxicity reported in prior studies in male rats, our data suggest a species difference between rats and mice in terms of susceptibility to CF3I-induced thyroid hormone perturbation.

Natural Fibre Polymer Composites – A Game Changer for the Aviation Sector?

As part of the efforts to reduce the environmental impacts caused by the aviation sector, the use of bio-based instead of fossil-based materials has been assessed as a possible mitigation option. Natural Fibre Polymer Composites have proven to have a higher environmental performance in the automotive sector and are emerging as an option for weight reduction in aircraft. This study quantifies, though Life Cycle Assessment, the environmental performance of specific flax-based composite panels intended for aircrafts as interior fitting elements (i.e. partition panels, tray tables, baggage compartments) compared to a glass fibre/epoxy composite with a honeycomb core. Through system expansion, the fate of co-products issued from the production of the flax fibre technical textile used as reinforcement in the biocomposite material were considered in the assessment. Results showed that for an application in the aeronautics sector, the weight of the panels is the upmost critical parameter shaping the overall environmental performance of panels. Focusing on the panel production only, the biocomposite panel showed a higher environmental performance in the categories of climate change and marine eutrophication compared to the conventional panel, and the fire suppressant agent was identified as the main contributor to the environmental impacts of the bio-based panel. Yet these gains were negligible when considering the full life cycle of the panels, due to the higher weight (14%) of the bio-based panels; which is linked to the bio-based panel being at a prototype stage.In order to improve the environmental performance of the biocomposite panel and thus reduce its weight, it was shown relevant to optimize geometry of the panel itself, especially its core, so less resin could be used.

Machinery Space Fire Fighting – Modern Alternatives

Machinery spaces in the majority of Royal Navy (RN) vessels use carbon dioxide (CO2) as the primary fire suppressant. While CO2 is very effective for firefighting, particularly in machinery space application, it is harmful to life in the concentrations required for effective fire suppression; exposure to concentrations greater than 15% can cause death within sixty seconds. The use of CO2 and similar fire suppressant systems in machinery spaces presents a risk due to the potential exposure of personnel. This may occur in a fire scenario where personnel are unable to escape the affected compartment, if there is a leak in the system, or due to accidental discharge. These risks are typically mitigated through physical means and procedural controls. However, in the hierarchy of safety controls the primary means should always be the elimination of the hazard. Babcock Energy and Marine undertook a study for the United Kingdom Ministry of Defence (MoD) into alternative methods of firefighting on Royal Navy minor warship machinery spaces with the safety of personnel considered a key requirement. The study identified five alternatives to CO2 available on the market. One particular aerosol fire suppression system was found to be superior to the others for application in small craft. This system is not toxic, non-ozone depleting and leaves almost no residue after application to the affected space, enabling re-entry (provided that the space has been ventilated to remove the products of combustion). The study concluded that traditional methods of fire suppression should be reconsidered across all small craft due to the health and safety issues associated with CO2 and the availability of improved alternatives. This paper considers the use of traditional firefighting systems on naval vessels in light of 21st century health and safety regulations. An assessment of current fire extinguishing agents is presented followed by a case study to determine the most appropriate solution for a minor warship concept with a particular aerosol system being justified as the preferred option. The paper also considers if the same conclusions would be reached for major warships or if the difference in scale results in an alternative solution.