Temperature-controlled airflow ventilation in operating rooms compared with laminar airflow and turbulent mixed airflow.

AIM: To evaluate three types of ventilation systems for operating rooms with respect to air cleanliness [in colony-forming units (cfu/m3)], energy consumption and comfort of working environment (noise and draught) as reported by surgical team members. METHODS: Two commonly used ventilation systems, vertical laminar airflow (LAF) and turbulent mixed airflow (TMA), were compared with a newly developed ventilation technique, temperature-controlled airflow (TcAF). The cfu concentrations were measured at three locations in an operating room during 45 orthopaedic procedures: close to the wound (<40cm), at the instrument table and peripherally in the room. The operating team evaluated the comfort of the working environment by answering a questionnaire. FINDINGS: LAF and TcAF, but not TMA, resulted in less than 10cfu/m3 at all measurement locations in the room during surgery. Median values of cfu/m3 close to the wound (250 samples) were 0 for LAF, 1 for TcAF and 10 for TMA. Peripherally in the room, the cfu concentrations were lowest for TcAF. The cfu concentrations did not scale proportionally with airflow rates. Compared with LAF, the power consumption of TcAF was 28% lower and there was significantly less disturbance from noise and draught. CONCLUSION: TcAF and LAF remove bacteria more efficiently from the air than TMA, especially close to the wound and at the instrument table. Like LAF, the new TcAF ventilation system maintained very low levels of cfu in the air, but TcAF used substantially less energy and provided a more comfortable working environment than LAF. This enables energy savings with preserved air quality.

Validation of an air-liquid interface toxicological set-up using Cu, Pd, and Ag well-characterized nanostructured aggregates and spheres.

ABSTRACT: Systems for studying the toxicity of metal aggregates on the airways are normally not suited for evaluating the effects of individual particle characteristics. This study validates a set-up for toxicological studies of metal aggregates using an air-liquid interface approach. The set-up used a spark discharge generator capable of generating aerosol metal aggregate particles and sintered near spheres. The set-up also contained an exposure chamber, The Nano Aerosol Chamber for In Vitro Toxicity (NACIVT). The system facilitates online characterization capabilities of mass mobility, mass concentration, and number size distribution to determine the exposure. By dilution, the desired exposure level was controlled. Primary and cancerous airway cells were exposed to copper (Cu), palladium (Pd), and silver (Ag) aggregates, 50-150 nm in median diameter. The aggregates were composed of primary particles <10 nm in diameter. For Cu and Pd, an exposure of sintered aerosol particles was also produced. The doses of the particles were expressed as particle numbers, masses, and surface areas. For the Cu, Pd, and Ag aerosol particles, a range of mass surface concentrations on the air-liquid interface of 0.4-10.7, 0.9-46.6, and 0.1-1.4 µg/cm2, respectively, were achieved. Viability was measured by WST-1 assay, cytokines (Il-6, Il-8, TNF-a, MCP) by Luminex technology. Statistically significant effects and dose response on cytokine expression were observed for SAEC cells after exposure to Cu, Pd, or Ag particles. Also, a positive dose response was observed for SAEC viability after Cu exposure. For A549 cells, statistically significant effects on viability were observed after exposure to Cu and Pd particles. The set-up produced a stable flow of aerosol particles with an exposure and dose expressed in terms of number, mass, and surface area. Exposure-related effects on the airway cellular models could be asserted.

Methodology for identifying particle sources in indoor environments.

Growing concern about airborne particles in indoor environments requires fast source identification in order to apply remedial actions. A methodology for identifying sources emitting particles larger than 0.5 microm was designed and applied. It includes: (1) visual inspection of interior surfaces in order to identify deposited particles and inspection of potential sources (equipment, materials, activities etc.) of airborne particles. (2) Technical measurements of airborne particles at different positions in a building with simultaneous logging of activities. (3) Isolating potential activities/particle sources in a test chamber, initially free from particles, for controlled characterizations of the particles generated. The methodology was applied in a study of three houses in southern Sweden. The results show that source identification is facilitated by knowledge of concentration variations between different rooms, real-time measurements together with activity reports and information on particle characteristics that are comparable with results from laboratory simulations. In the houses to which the methodology was applied, major particle emissions from textile handling were identified, which were likely due to detergent zeolite residues.

Airborne particle deposition onto the ocular surface.

UNLABELLED: Eye irritation is one of the most frequently reported symptoms in relation to working in office-like environments. So far, no consistent association has been found between concentration of airborne particles and prevalence of eye irritation. External physical factors not hitherto considered could have a large influence on particle deposition velocity onto the ocular surface. This may have obscured the role airborne particles play. Based on previously published semi-empirical models, the paper describes the influence of turbulence, gravitational settling, electrical fields, and thermophoresis on deposition velocity. A probabilistic approach was used to determine percentile ranges in deposition velocity when the magnitude of these parameters varied within typical ranges. The calculations suggest that differences in external factors other than particle size may cause differences in the deposition velocity of one order of magnitude or more. Studies trying to find associations between airborne particle concentration levels and eye irritation should take into consideration the influence of external physical factors on deposition velocity. PRACTICAL IMPLICATIONS: External physical factors other than concentration are likely to have a large influence on the deposition rate of airborne particles onto the ocular surface. Thus, future studies on associations between airborne particle levels and eye symptoms should only be conducted if particle concentration measurements are suitably size resolved. Other relevant external physical factors should also be assessed and included in a multivariate analysis of exposure-response associations.

'EUROPART'. Airborne particles in the indoor environment. A European interdisciplinary review of scientific evidence on associations between exposure to particles in buildings and health effects.

The relevance of particle mass, surface area or number concentration as risk indicators for health effects in non-industrial buildings has been assessed by a European interdisciplinary group of researchers (called EUROPART) by reviewing papers identified in Medline, Toxline, and OSH. Studies dealing with dermal effects or cancer or specifically addressing environmental tobacco smoke, house dust-mite, cockroach or animal allergens, microorganisms and pesticides were excluded. A total of 70 papers were reviewed, and eight were identified for the final review: Five experimental studies involving mainly healthy subjects, two cross-sectional office studies and one longitudinal study among elderly on cardiovascular effects. From most studies, no definite conclusions could be drawn. Overall, the group concluded that there is inadequate scientific evidence that airborne, indoor particulate mass or number concentrations can be used as generally applicable risk indicators of health effects in non-industrial buildings and consequently that there is inadequate scientific evidence for establishing limit values or guidelines for particulate mass or number concentrations.

Characterization of thermally generated aerosols from polyurethane foam.

Isocyanates constitute a group of highly reactive chemicals used on a large scale for the production of flexible polyurethane (PUR) foam. Exposure to isocyanates is known to produce irritation of the mucous membranes and the eyes. Isocyanates also have strong sensitizing properties and may cause occupational asthma. It is therefore important to monitor isocyanate emissions at workplaces. To obtain information for the improvement of isocyanate samplers and for health risk assessments of exposure, the emitted aerosol from two types of flexible PUR foam subjected to thermal degradation was characterized. Particle size distribution and toluene diisocyanate (TDI) concentration in the emitted aerosols were measured. Thermal degradation of flexible PUR foam at temperatures from 250 to 300 degrees C produced an aerosol with a geometric mean particle diameter of 30-50 nm. Between 5% and 9% of the PUR foam was emitted as TDI, and 2% to 6% of TDI monomers were found in the particle phase under the experimental conditions used. The 2,6-TDI isomer was more abundant in the gas phase than in the particle phase.

Bronchocarcinogenic properties of welding and thermal spraying fumes containing chromium in the rat.

The possible bronchocarcinogenic effects of fumes released during the shielded metal arc welding of stainless steel and the thermal spraying of chromium oxide (Cr2O3) have been studied on the rat. The fume particles were shown to contain tri- and hexavalent chromium in soluble and low soluble forms; they were collected and implanted as pellets in the bronchi of groups of 100 rats by the method of Laskin et al. A negative control group of 100 rats was included, as well as positive controls receiving pellets containing benz(a)pyrene. The experiment was continued for 34 months; no differences of biological significance were noted between the growth rates, survival times, and terminal organ weights of the test and negative control groups. At autopsy, the macroscopic and microscopic appearance of the organs in the three groups, including the local reaction to the implanted pellet, were similar. No precancerous changes were observed at the implantation sites; one rat, who received a pellet containing welding fumes, showed squamous cell carcinoma remote from the implantation site and not associated with the bronchus. It had the appearance of a metastasis. All three benz(a)pyrene control rats developed cancer at the implantation site. The occupational health implications of these findings are discussed.