Containment testing of laboratory hoods in the as-used condition.

Airborne contaminants generated inside laboratory fume hoods during use leak into the breathing zone of the user. Concentration of the leakage is unknown and variable depending on laboratory design, work practices, arrangement of internal apparatus, face velocity, and sash height. Surrogate tracer gas tests have been developed using sulfur hexafluoride (SF6) and a manikin to estimate leakage. This study presents results of hood leakage tests using SF6 with a manikin and then a live operator performing a phenol:chloroform (P:C) extraction. Four hoods were tested in each of three institutions during normal work hours with the lab occupied. The purpose of the study was to determine leakage concentrations for the SF6-manikin with effects of sash height, hood contents as found and after being cleaned out, face velocity, and the actual P:C and SF6 exposure concentrations of the user during work. Results indicate P:C was not detectable in the breathing zone of the 12 operators (< 0.1 ppm) at their selected operating sash heights (7 to 15 inches). Simultaneous SF6 concentrations were also minimal (average 0.06 ppm). Average leakage was 0.02 percent for SF6 and less than 2 percent based on chloroform concentrations measured in the breathing zone of the operator and inside the hood. SF6 percent leakage was greater when sash height was above the breathing zone of the manikin (average 2.09 percent) and lower leakage (average 0.02 percent) when below the breathing zone (26 inches or less). Average face velocity did not appear to be a predictor of average hood leakage. Cleaning out the hoods did not reduce leakage in most tests. The data from this study shows that when providing training on proper work practices for lab hood use, lowering the sash should be stressed as being the major factor in reducing hood leakage.

Consensus radiation protection practices for academic research institutions.

Under the auspices of the Howard Hughes Medical Institute, a set of consensus guidelines for Radiation Protection Practices has been developed for biomedical research using radioactive materials. The purposes of the guidelines are (1) to promote good radiation protection practices consistent with the needs of biomedical research, the ALARA principle, and regulatory requirements; (2) to establish common goals and consistent practices within radiation safety programs; and (3) to build a meaningful partnership between radiation safety professionals and the biomedical research community. These practices are intended to enhance radiation protection and the efficiency of the research staff. The consensus guidelines will lessen the variability in radiation safety practices that is evident among many academic research institutions and will encourage better acceptance and regulatory compliance by users of radioactive materials in biomedical research.

Howard Hughes Medical Institute dose assessment survey.

Biomedical science researchers often express frustration that health physics practices vary widely between individual institutions. A survey examining both internal and external dose assessment practices was devised and mailed to fifty institutions supporting biomedical science research. The results indicate that health physics dose assessment practices and policies are highly variable. Factors which may contribute to the degree of variation are discussed.

Risk of human immunodeficiency virus (HIV-1) infection among laboratory workers.

In a prospective cohort study of 265 laboratory and affiliated workers, one individual with no recognized risk factors for human immunodeficiency virus type 1 (HIV-1) infection was HIV-1 seropositive at the time of entry into the study. Molecular analyses of two HIV-1 isolates derived in two independent laboratories from a blood sample from this worker showed that the isolates were indistinguishable from a genotypic form of HIV-1 present in the H9/HTLV-IIIB cell line. Exposure to this strain of virus most probably occurred during work with concentrated virus or culture fluids from virus-producing cell lines under standard Biosafety Level 3 containment. Although no specific incident leading to this infection has been identified, undetected skin contact with virus culture supernatant might have occurred. This worker was the only one found to be positive among the subgroup of 99 workers who shared a work environment involving exposure to concentrated virus. The incidence rate of 0.48 per 100 person-years exposure indicates that prolonged laboratory exposure to concentrated virus is associated with some risk of HIV-1 infection, which is comparable to the risk for health care workers experiencing a needle stick exposure. While none of the ten workers with parenteral exposure to HIV-1 in this cohort became infected, a worker in another laboratory did seroconvert following an injury with a potentially contaminated needle. Strict Biosafety Level 3 containment and practices should be followed when working with concentrated HIV-1 preparations, and further refinement of the procedures may be necessary.