Retrospective study of pneumonia due to Panton-Valentine leukocidin-producing Staphylococcus aureus in Reunion.

OBJECTIVE: Panton-Valentine leukocidin-producing Staphylococcus aureus necrotizing pneumonia is an unusual cause of community-acquired pneumonia, although associated with a high case fatality. This infection mainly affects young individuals, without any history, and is most often preceded by flu-like symptoms. METHOD: We focused on patients presenting with Staphylococcus aureus necrotizing pneumonia in Reunion (Indian Ocean) admitted to the emergency department. We performed a retrospective study based on data collected from laboratory registers and medical files of patients presenting with Staphylococcus aureus necrotizing pneumonia in Reunion between December 2014 and December 2017. RESULTS: A total of 16 patients were recruited for this study, with a median age of 40.5 years. More than half of patients had previously been admitted to the emergency department for acute respiratory distress syndrome or severe sepsis. Fourteen patients were admitted to the intensive care unit and six patients died (five premature deaths). CONCLUSION: Physicians should be aware of this infection during the flu season and quickly adapt the specific antibiotic treatment, including a drug inhibiting toxin production. As methicillin-resistant Staphylococcus aureus is very rarely observed in Reunion, physicians can still adapt the empirical treatment, without glycopeptides.

Is the radon risk overestimated? Neglected doses in the estimation of the risk of lung cancer in uranium underground miners.

Only the exposure to inhaled radon decay products is usually taken into account in the determination of the risk of radiogenic lung cancer in uranium miners. However, the elevated lung cancer risk in uranium miners is due to the total dose of radiation received by that organ, not to the dose from inhaled radon-222 decay products (222Rn D.P.) alone. Lung doses from sources other than 222Rn D.P. may reach 25% to 75% of total effective dose, absorbed dose or equivalent lung dose, are correlated to 222Rn D.P. doses and are quite variable between facilities. Therefore, to neglect these doses leads to a systematic overestimation of the risk of lung cancer per unit 222Rn D.P. exposure, both through dose underestimation and dose misclassification. Correction for neglected doses and dose misclassification would pull the risk per unit radon exposure downward by a factor of at least two or three and bring the overall dose-effect relationship towards the no-effect null hypothesis, thereby increasing the likelihood of thresholds for lung cancer risk at indoor and today's uranium mine exposures.

Characterization of long-lived radioactive dust in uranium mill operations.

The characteristics of long-lived radioactive dust clouds generated in several mechanical and physiochemical operations in a uranium mill have been investigated. The study consisted of the determination of dust size distribution and of the size distribution of radionuclides associated with particulate matter in the size range less than 0.1 to 26 microns. Experiments were conducted by using two different types of cascade impactors operating at different sampling flow rates. Radionuclide identification was done by using alpha-spectrometry. Long- and short-lived radionuclides were identified in dust samples. The characteristics of the dust clouds depended on the mill operation, such as crushing (vibrating grizzly, jaw crusher, cone crusher); screening; ore transportation; grinding; acid leaching; counter-current decantation; yellow cake precipitation and drying; and yellow cake packaging. In addition, other dust and radioactivity measurements have been carried out.

Implications of dose distribution on monitoring requirements in U mines and mills.

In U mines and mills, mean doses from gamma radiation and 222Rn daughters, respectively, range from 10-30% of the individual limits recommended by the International Commission on Radiological Protection (ICRP), while the mean exposure to long-lived dust can be as low as a few percent or as high as 30% of the ICRP recommended limit. In certain mines, 220Rn daughters are present and should also be measured and accounted for. When the doses (or dose equivalents) from all the components of the radiation sources are taken into account, according to the ICRP notions of effective dose equivalent and committed effective dose equivalent, the mean of the combined doses can reach 30-50% of the combined permissible limit of dose. It is generally observed that individual doses and exposure to radiation are log-normally distributed. Since individual exposures to each specific hazard are generally not correlated, there is a probability that a number of individuals belong to the upper part of each exposure distribution. Therefore, it can happen that non-negligible fractions of the populations are liable to be close to the combined dose limit or to be overexposed. Consequently, in view of the observed nature of the distributions and the need to account for all sources of radiation, it is essential that appropriate radiation monitoring techniques be used to measure and record all significant doses and exposures. The analysis of the results of appropriate monitoring practices will lead to improved engineering controls of radiation hazards and optimum use of preventive resources.