Deborah Salzberg

Increased levels of bacterial markers and CO2 in occupied school rooms

Our group previously demonstrated that carbon dioxide (CO2) levels in heavily occupied schools correlate with the levels of airborne bacterial markers. Since CO2 is derived from the room occupants, it was hypothesized that in schools, bacterial markers may be primarily increased in indoor air because of the presence of children; directly from skin microflora or indirectly, by stirring up dust from carpets and other sources. The purpose of this project was to test the hypothesis. Muramic acid (Mur) is found in almost all bacteria whereas 3-hydroxy fatty acids (3-OH FAs) are found only in Gram-negative bacteria. Thus Mur and 3-OH FA serve as markers to assess bacterial levels in indoor air (pmol m(-3)). In our previous school studies, airborne dust was collected only from occupied rooms. However, in the present study, additional dust samples were collected from the same rooms each weekend when unoccupied. Samples were also collected from outside air. The levels of dust, Mur and C10:0, C12:0, C14:0, and C16:0 3-OH FAs were each much higher (range 5-50 fold) in occupied rooms than in unoccupied school rooms. Levels in outdoor air were much lower than that of indoor air from occupied classrooms and higher than the levels in the same rooms when unoccupied. The mean CO2 concentrations were around 420 parts per million (ppm) in unoccupied rooms and outside air; and they ranged from 1017 to 1736 ppm in occupied rooms, regularly exceeding 800-1000 ppm, which are the maximum levels indicative of adequate indoor ventilation. This indicates that the children were responsible for the increased levels of bacterial markers. However, the concentration of Mur in dust was also 6 fold higher in occupied rooms (115.5 versus 18.2 pmole mg(-1)). This further suggests that airborne dust present in occupied and unoccupied rooms is quite distinct. In conclusion in unoccupied rooms, the dust was of environmental origin but the children were the primary source in occupied rooms.

Systematic Review of Chromium and Nickel Exposure During Pregnancy and Impact on Child Outcomes

Some forms of chromium (Cr) and nickel (Ni) are toxic, especially with chronic elevated exposure, and certain forms such as hexavalent chromium or nickel carbonyl were labeled as carcinogens. Since both metals are naturally occurring, and used in industrial processes, individuals may be exposed through ingestion of contaminated food or water, inhalation, or dermal contact. This study focused on the impact of toxic forms of Cr and Ni during pregnancy and outcomes in newborn and young children. A systematic literature review following “The Navigation Guide” was applied, and 16 reports that satisfied the inclusion criteria were scored. Six papers studied birth weight, prematurity, or gestational age: one found an association between Ni and small for gestational age, while another linked Ni with low birth weight; however, four reported no marked associations. Of six studies that examined birth defects, three found no significant associations; one noted an association between Ni and neural tube defects; one showed an association between Ni and structural birth defects; and one reported a weak effect for Cr exposure and musculoskeletal defects. In the remaining four studies, weak associations were found for hexavalent Cr and neuroblastoma, Ni and autism spectrum disorder, Cr and Ni and DNA damage, and Cr and lymphocyte damage. Among the studies that were rated as good for execution and reliability, there was weak evidence of an association between Ni and autism spectrum disorder and small for gestational age, but no significant association between Cr and a child outcome.

Deriving Realistic Source Boundary Conditions for a CFD Simulation of Concentrations in Workroom Air

Computational fluid dynamics (CFD) is used increasingly to simulate the distribution of airborne contaminants in enclosed spaces for exposure assessment and control, but the importance of realistic boundary conditions is often not fully appreciated. In a workroom for manufacturing capacitors, full-shift samples for isoamyl acetate (IAA) were collected for 3 days at 16 locations, and velocities were measured at supply grills and at various points near the source. Then, velocity and concentration fields were simulated by 3-dimensional steady-state CFD using 295K tetrahedral cells, the k-ε turbulence model, standard wall function, and convergence criteria of 10(-6) for all scalars. Here, we demonstrate the need to represent boundary conditions accurately, especially emission characteristics at the contaminant source, and to obtain good agreement between observations and CFD results. Emission rates for each day were determined from six concentrations measured in the near field and one upwind using an IAA mass balance. The emission was initially represented as undiluted IAA vapor, but the concentrations estimated using CFD differed greatly from the measured concentrations. A second set of simulations was performed using the same IAA emission rates but a more realistic representation of the source. This yielded good agreement with measured values. Paying particular attention to the region with highest worker exposure potential-within 1.3 m of the source center-the air speed and IAA concentrations estimated by CFD were not significantly different from the measured values (P = 0.92 and P = 0.67, respectively). Thus, careful consideration of source boundary conditions greatly improved agreement with the measured values.

A Second Look at the Palmes’ Diffusive Sampler

Abstract The Palmes’ tube, the first diffusive sampler incorporating a fixed path length, has received wide usage for the sampling of a large number of gaseous pollutants. But despite numerous previous studies, questions remain regarding the accuracy of these inexpensive, simple-to-construct, open-ended samplers. Here the mass transfer resistance in a Palmes’ diffusive sampler was measured using the loss of cyclohexane from a Palmes’ tube containing liquid cyclohexane at its base. The average loss rates, at factorial combinations of five air incidence angles evenly spaced from 270° to 90°, and five air speeds from 0.5 m/sec to 2.5 m/sec ranged from 46% to 121% higher than rates calculated from the physical dimensions of the sampler, proving the need to calibrate these samplers rather than relying on a theoretical calculation. The mass transfer resistance was nearly constant when the airflow was perpendicular to the sampler and sufficiently high to avoid stagnation, a finding that may explain the widespread acceptance of the results obtained using this sampler.

Development of a tool to describe overall health, social independence and activity limitation of adolescents and young adults with disability

There is a need for research that focuses on the correlation between self-perceived quality of life (QoL) and the health outcomes of adolescents with disability transitioning to adulthood. To better understand the transition experience of adolescents and young adults with disability, we developed a questionnaire to assess the impact of disability on QoL. We recruited 174 participants who were 15-24 years old and diagnosed with Fragile X syndrome (FXS), spina bifida (SB) or muscular dystrophy (MD) and conducted an exploratory factor analysis to identify factors that characterize QoL. Five factors emerged: emotional health, physical health, independence, activity limitation, and community participation. To validate the tool, we linked medical claims and other administrative data records and examined the association of the factor scores with health care utilization and found the questionnaire can be utilized among diverse groups of young people with disability.

Differences in Race and Ethnicity in Muscular Dystrophy Mortality Rates for Males under 40 Years of Age, 2006–2015

Background/Aims: Duchenne Muscular Dystrophy (DMD) has childhood onset, primarily affects males, and is usually fatal before the age of 40 years. Previous studies have indicated that this X-linked condition is more prevalent in whites than in blacks, but those were based on active surveillance, and limited to smaller populations and younger ages. Methods: US death data were used to calculate mortality rates by race and ethnicity, with MD as either the underlying or multiple cause of death (MCD). Poisson approximation was used for confidence intervals; chi-square was used to compare rates. Results: From 2006 to 2015, there were 3,256 deaths in males <40 years with MD as MCD, and 71% of these were aged 15–29 years. For whites, the average annual death rate was 0.43/100,000, which was significantly higher (p < 0.0001) that that of blacks (0.28), American Indian/Alaska Natives (0.20), and Asian/Pacific Islanders (0.21). The rate for non-Hispanic whites (0.46) was significantly higher (p < 0.0001) than the rates for Hispanic whites (0.31), Hispanic blacks (0.07), and non-Hispanic blacks (0.29). Conclusion: Since DMD is the primary cause of deaths in young males with MD, mortality rates are a reasonable proxy for the relative difference in racial prevalence. It appears that DMD is significantly more common in white males than in males of other races.

Experimental tests of copper components in ventilation systems for microbial control

Colonization of HVAC systems by microbes may lead to release of hazardous bioaerosols containing allergens, irritants, odorants, or infectious agents to indoor air, possibly adversely affecting system performance. Unlike the many common materials used in HVAC systems, copper and copper alloys have been shown in laboratory investigations to kill bacteria and fungi on contact after several hours. This study tested coppers antimicrobial properties in comparison with aluminum in full-scale, carefully controlled air-conditioning systems, four with copper heat exchanger assemblies and four with aluminum assemblies, at identical airflow rates, temperatures, humidity, and input microbe levels. Fungal and bacterial loads on copper surfaces in heat exchangers were lower than on aluminum surfaces by factors of 3500 and more than 500, respectively, over a 4-month period. No statistically significant difference in the release of airborne microbes was detected between copper and aluminum heat exchangers. The moderate conditions employed in this study, while still within the range commonly found in HVAC systems, possibly prevented the high microbial loading on aluminum heat exchanger surfaces from translating into significant differences in airborne concentrations between copper and aluminum systems.