Development of a continuous aerosol mass concentration measurement device.

A dynamic aerosol mass concentration measurement device has been developed for personal sampling. Its principle consists in sampling the aerosol on a filter and monitoring the change of pressure drop over time (Delta P). Ensuring that the linearity of the Delta P = f(mass of particles per unit area of filter) relationship has been well established, the change of concentration can be deduced. The response of the system was validated in the laboratory with a 3.5 microm alumina aerosol (mass median diameter) generated inside a 1-m(3) ventilated enclosure. As the theory predicted that the mass sensitivity of the system would vary inversely with the square of the particle diameter, only sufficiently fine aerosols were able to be measured. The system was tested in the field in a mechanical workshop in the vicinity of an arc-welding station. The aerosol produced by welding is indeed particularly well-adapted due to the sub-micronic size of the particles. The device developed, despite this limitation, has numerous advantages over other techniques: robustness, compactness, reliability of calibration, and ease of use.

Changes in the performances of filter media during clogging and cleaning cycles.

The performance of two filter media used in industrial air cleaning were studied both in the initial state (new filter) and after a number of collection and pulse pressure cleaning cycles. The main difference between them is that one has anti-clogging properties and the other does not. The test aerosol is composed of alumina particles with a median volumetric diameter of 2.6 microm (MMAD=4.8 microm) generated at a concentration of 700 mg x m(-3). Filtration took place at a velocity of 2 cm x s(-1). Two parameters, namely pressure drop and efficiency, were monitored according to the collection and cleaning cycles. The comparison of the filtration efficiency of the two media and that of the corresponding industrial dust separator at the end of the cycles showed a close agreement. The separation efficiency calculated with a new medium (corresponding to initial switch-on of the installation) was low and increased very quickly during the cycles. Finally, a phenomenological model was developed to represent the increase in pressure drop of a filter medium after cleaning and was found to be in close agreement with the experimental values.

[Seroprevalence of hepatitis C antibodies among blood donors. Study of second generation ELISA and RIBA tests and surrogate markers]. / Séroprévalence des anticorps contre le virus de l'hépatite c chez les donneurs de sang. Etude des tests ELISA et RIBA de 2e génération et des marqueurs indirects.

Between March and November 1991, prevalence of hepatitis C antibodies was evaluated in 60,960 blood donors from the North-East of France. Using a second generation ELISA, 424 donors (0.69%) were reactive, with no significant difference between males (0.69%) and females (0.70%). Among these 424 donors, respectively 137 (32.3%), 86 (20.3%) and 201 (47.4%) were reactive, indeterminate or nonreactive by a second generation RIBA (RIBA-2) (Recombinant Immunoblot Assay). Donors with a high ELISA ratio (> or = 4) were significantly more likely to have a reactive RIBA-2. Of the 1906 donors with anti-HBc positivity (3.12%), 44 had a reactive ELISA; of these, respectively 27, 12 and 5 had a reactive, indeterminate and nonreactive RIBA. Of the 1201 donors (1.97%) with increased serum ALAT (alanine-amino-transferase) levels (> or = 2N), 42 had a positive ELISA; of these, respectively 35, 2 and 5 had a reactive, indeterminate and nonreactive RIBA. Of the 54 donors with both indirect markers, nine had a reactive ELISA; the same nine donors had a reactive RIBA. These data show that donors with both surrogate markers and a reactive ELISA are very likely to have a positive RIBA. Seventy-seven (18.16%) of the 424 donors with a reactive ELISA had at least one surrogate marker; 67 of these donors (30.04%) were among the 223 donors with a reactive ELISA and a reactive or indeterminate RIBA.

[Epidemiologic study of HIV serology in blood donors from 5 departments in northeastern France (1985-1989)]. / Etude épidémiologique de la sérologie VIH des donneurs de sang dans cinq départements du nord-est de la France (1985-1989).

Between July 1985 and June 1989, the prevalence of HIV antibody was studied in 503,019 blood donations tested in 5 administrative areas ("departments") of north east France: 91 seropositive donations (donors) were detected (prevalence: 0.18%). The prevalence was 0.41% in 1985, 0.22% in 1986, 0.14% in 1987, 0.10% in 1988 and 0.11% in 1989: in each year, it was found lower than the national prevalence. 14 (15.4%) of the 91 seropositive donors were females, and the prevalences of HIV antibody in blood donations from female and male donors were 0.07% and 0.26% respectively. All seropositive donors were younger than 50 and 83 (91.2%) younger than 40. The prevalence of HIV antibody was higher in blood units at first donation (occasional donors) as compared with blood units collected from regular donors (0.60% versus 0.09%). The prevalence of HIV antibody was higher in blood donations from military donors as compared with donations from civilian donors (0.49% versus 0.07% in 1987, 1988 and 1989). Most seropositive military donors were young male recruits of the national armed forces conscription system. We believe that these recruits are subjects with risk factors which must be taken into account for the determination of national blood supply policies.