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PubMed2002

Breast cancer cell contamination of blood stem cell products in patients with metastatic breast cancer: predictors and clinical relevance.

The incidence and clinical relevance of tumor cells contaminating the stem cell products of patients with advanced breast cancer treated with high-dose chemotherapy is uncertain because prior studies used small sample sizes and lacked standardization of the immunocytochemistry (ICC) detection method used. We evaluated blood stem cell and bone marrow samples obtained from 535 women with metastatic breast cancer who received high-dose chemotherapy and unmanipulated mobilized blood stem cell support. Of the patients tested, 20.6% and 26.3% had blood stem cell and bone marrow contamination, respectively. Blood stem cell contamination was significantly more frequent in patients with marrow involvement than in patients without marrow involvement (35% versus 18.4%, respectively; P = .009). In fact, according to multivariate analysis results, marrow involvement was the only significant predictor for blood stem cell product contamination. Patients without marrow involvement who had fewer apheresis procedures were also observed to have a significantly lower incidence rate of blood stem cell contamination than patients who had more procedures (P < or = .008), and patients who received combined chemotherapy and cytokine mobilization therapy had less contamination than patients who received cytokine alone (P = .0001). Combined mobilization therapy appears to be associated with a lower incidence of contamination as a result of fewer apheresis procedures rather than through an antitumor effect of chemotherapy (P < or = .001). Patients with ICC-negative blood stem cell products had significantly longer progression-free survival (PFS) and overall survival (OS) than did patients with ICC-positive blood stem cell products (median PFS, 401 versus 291 days, respectively, P = .007; median OS, 1060 versus 697 days, P = .009) . However, multivariate analysis did not reveal any significant independent predictors of survival outcomes. Thus, further study is needed to determine if contaminating tumor cells in the stem cell products of breast cancer patients ever directly impact survival outcomes or are only indicative of residual in vivo disease in high-dose chemotherapy recipients.

Adult↗

PubMed1992

[B-streptococci in obstetrics--risks and consequences of maternal colonization and neonatal contamination].

2,373 mothers and their newborn were studied during two years with respect to B streptococci colonisation or contamination. Bacteriological, vaginal and anal smears were taken from mothers at the beginning of parturition, as well as the amnion and the aspirated stomach contents of the newborn, employing, in each case, conventional culture methods and a latex agglutination test as a rapid testing method. Smears from the ears were also taken from the newborn for bacteriological examination. The vertical transmission and its possible influencing variables were examined in 1,328 mother/child pairs of the first observation year. Surface contamination of the newborn was confirmed in 10% in at least one smear. In the group of mothers with B streptococci colonisation, the amnion showed the highest rate of contamination (43%), followed by the aspirated stomach contents (26%) and the ear smears (taken from each side separately) with 28% and 30% respectively. Vertical transmission was decisively influenced by vaginal maternal colonisation (50% of the cases resulting in contamination of newborn), whereas anal colonisation, if it was the only site of colonisation, resulted in contamination of newborn in only 32% of the cases. The rate of contamination of newborn dropped significantly from 50% to 20% after intrapartal antibiotic prophylaxis, the latter appearing to be meaningful only after at least 6 hours of exposure. In this group, the surface contamination could be reduced from 61% to 8%. A group of newborn suffering from early onset of sepsis (0.4%), was compared with a group of 13 newborn at risk of infection (0.9%) with established surface contamination and clinical or laboratory chemistry confirmation of infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Ampicillin↗

PubMed2003

The effect of blood contamination on the shear bond strength of orthodontic brackets with the use of a new self-etch primer.

The success of bonding brackets to enamel with resin bonding systems is negatively affected by contamination with oral fluids such as blood and saliva. The new self-etch primer systems combine conditioning and priming agents into a single application, making the procedure more cost-effective. The purpose of this study was to assess the effect of blood contamination on the shear bond strength of orthodontic brackets with a new self-etch primer. The brackets (precoated brackets APC II, 3M Unitek, Monrovia, Calif) were bonded to 52 extracted human molars according to 1 of 4 protocols. Group I: A self-etch acidic primer, Angel I (3M/ESPE, St. Paul, Minn), was placed on the enamel for 15 seconds, gently dried with air, and light cured for 10 seconds. Brackets were bonded and light cured for 20 seconds. Group II: The enamel surface was contaminated with human blood for 10 seconds, and the blood was blown off with an air syringe for 5 seconds. Angel I was applied on the contaminated surface; the brackets were then bonded and light cured as in group I. Group III: Angel I was applied as described in group I. The surface was then contaminated with human blood for 10 seconds, and the blood was blown off with an air syringe for 5 seconds. Precoated brackets were then bonded as in groups I and II. Group IV: The enamel surface was contaminated with human blood for 10 seconds and blown off with an air syringe for 5 seconds. The self-etch primer, Angel I, was applied as described earlier, and the surface was recontaminated with human blood for 10 seconds, and the blood was blown off with an air syringe for 5 seconds. The brackets were then bonded as in groups I, II, and III. The results of the analysis of variance (F = 13.31) indicated that the shear bond strengths of the 4 groups were significantly different (P =.001). Tukey HSD posterior tests indicated that the uncontaminated control group had a significantly stronger (mean = 6.0 +/- 3.5 megapascal [MPa]) shear bond strength than the groups that had blood contamination, regardless of whether this occurred before (mean = 2.7 +/- 2.4 MPa), after (mean = 1.1 +/- 0.6 MPa), or before and after (mean = 0.5 +/- 0.2 MPa) the application of the self-etch primer. Blood contamination at any stage of the bonding procedure results in a significant and drastic drop in the shear bond strength of orthodontic brackets.

Acid Etching, Dental↗

PubMed2004

Water contamination in urban south India: household storage practices and their implications for water safety and enteric infections.

Water contamination, at source and during household storage, is a major cause of enterically transmitted infections in developing countries. This study assessed contamination of the municipal water in a south Indian town, which obtains its water intermittently from a surface lake and by pumping subsurface water from a dry river bed, and monitored microbial contamination during household storage. All samples of the 'treated' municipal water were contaminated when freshly pumped, and on household storage, 25/37 (67%) showed increased contamination during storage periods from 1 to 9 days. Household storage in brass, but not in containers of other materials significantly decreased contamination of water (p = 0.04). This was confirmed in the laboratory by testing water seeded with 10(3) to 10(5) Escherichia coli per 100 ml stored in containers of different materials (p < 0.01). Despite the requirements for provision of safe drinking water in municipal areas, in practice the water supplied in Vellore is contaminated and current household storage practices increase the level of contamination in at least two-thirds of households. The implementation of locally appropriate point-of-use disinfection and safe household storage practices in developing countries is an urgent need to ensure a safe, reliable year-round supply in areas where clean water is not available.

Adult↗

PubMed1996

The effect of different on-line dressing practices on microbiological and visible contamination of lamb carcasses.

Three dressing practices were assessed in traditional lamb carcass dressing systems for their ability to improve control of microbiological and visible contamination. The routine removal of a piece of skin from the perineal area reduced total aerobic plate counts and Escherichia coli counts on carcasses derived from both woolly and shorn groups of lambs. Similar results were found when the "Y-cut" was delayed in the dressing sequence, but E. coli counts increased slightly in one group. The use of a wide-blow shear prior to the opening cut on the hindleg of carcasses derived from woolly lambs resulted in a slight increase in the microbiological contamination on the leg. The removal of a piece of skin from the perineal area reduced scores for faecal contamination despite a small increase in contamination with wool. Changes in visible contamination in response to the two other dressing procedures were principally effected through changes in levels of contamination with wool. Irrespective of dressing procedures, levels of microbiological and visible contamination were lower on carcasses derived from shorn compared with woolly lambs. These studies demonstrated that, although they are reasonable indicators, the use of parameters of visible contamination as a measure of carcass hygiene must be treated with caution. This is especially the case if a genuine HACCP-based system for the control of dressing hygiene for a particular class of slaughtered livestock is to be implemented.

Journal Article↗

PubMed1984

Ultraviolet detection of synthetic oil contamination of skin.

A study was conducted to evaluate skin contamination occurring on coal liquefaction process workers using quantitative (Spill Spotter) and qualitative (blacklight) ultraviolet fluorescence methods. Other objectives were to determine the effectiveness of showering in removing contamination, and to determine the quantitative relationship between Spill Spotter response and skin contamination concentration. Field measurements showed wide ranges of background skin fluorescence caused by differing skin types. Visible dirt on the skin partially quenched the fluorescence response of the Spill Spotter. Fluorescent skin contamination on selected workers was quantified relative to a calibration curve developed on pigskin using a reference synfuel oil. One group of workers was shown to exhibit a two-to three-fold increase in fluorescence during the work shift. Showering removed skin contamination although residual contamination sometimes remained on workers that exhibited the greatest degree of skin contamination during the workshift. Further refinement of the ultraviolet method for absolute quantification of fluorescent skin contamination is needed.

Baths↗

PubMed1968

Lasting biological effects of early environmental influences. II. Lasting depression of weight caused by neonatal contamination.

Certain specific-pathogen-free (SPF) mice bred and maintained under semiprotected conditions have an intestinal flora which is qualitatively simpler (although not quantitatively smaller) than that of mice of the same genetic stock produced under ordinary conditions. They are also heavier at weaning time, grow at a faster rate, and reach a greater adult weight than ordinary mice. When SPF mice are contaminated per os shortly after birth with certain bacterial cultures isolated from the intestinal contents of adult ordinary mice, these bacteria multiply extensively throughout the gastrointestinal tract and persist at extremely high levels until weaning time. Such bacterial infections do not affect significantly either weaning weight, growth rate, or maximum adult weight. In contrast, weight depression could be consistently brought about by contaminating newborn SPF mice per os with bacteria-free filtrates of homogenates of intestines from ordinary mice. The weight-depressing agent passed through Millipore discs of 0.45 and 0.22 micro porosity, but was held back at 0.10 micro porosity. The depression of weight caused by either intestine homogenate or filtrates thereof could be detected within a few days after contamination (of 2 day old mice) and persisted throughout the adult life of the contaminated animals. When intestine homogenate of the SPF mice used in this study were introduced per os into newborn SPF mice, they did not affect their growth rate or adult weight. On several occasions, but not consistently, bacteria-free filtrates capable of depressing the weight curve of SPF mice produced alterations in the appearance of tissue cultures of BHK-21 and mouse embryo cells. When tissue cultures so infected were introduced into newborn SPF mice, the weight of these animals was depressed early and lastingly. An agent exhibiting weight-depressing activity has been transferred from mouse to mouse over many passages by contaminating newborn SPF animals per os. Weight depression was achieved with extremely small doses of material (10(-5) ml of intestine homogenate of 10(-4) of mouse embryo culture). Under these conditions, none of the animals showed obvious signs of disease except reduced weight. Only very young SPF mice (preferably less than 3 days old) proved susceptible to the weight-depressing effect of the filtrates of intestine homogenates or of infected tissue cultures prepared therefrom. After oral contamination, it took approximately 1 wk before the intestinal homogenate obtained from contaminated animals exhibited a high level of weight-depressing activity. The growth-depressing effect could be transmitted from one generation to the next by mating SPF mice that had been contaminated shortly after birth and that were consequently smaller than control SPF animals.

Animals↗

PubMed2006

Risk of environmental and healthcare worker contamination with vancomycin-resistant enterococci during outpatient procedures and hemodialysis.

OBJECTIVE: To assess the risk of environmental and healthcare worker (HCW) contamination with vancomycin-resistant enterococci (VRE) during outpatient procedures performed on fecally continent patients currently colonized with VRE (cVRE) or previously colonized with VRE (pVRE). DESIGN: Observational study. SETTING: Outpatient consultation and radiology rooms and the hemodialysis unit in a university teaching hospital. PATIENTS: Fecally continent cVRE and pVRE patients. INTERVENTIONS: Both cVRE and pVRE patients attended standardized mock outpatient consultations and routine hemodialysis sessions in an area that had been thoroughly cleaned and microbiologically confirmed to be free of VRE contamination. After each session, the patient, environment, and participating HCW were tested for VRE contamination. RESULTS: Fourteen cVRE patients participated in 49 mock outpatient consultation sessions and radiology sessions or 26 actual hemodialysis sessions, and 7 pVRE patients participated in 28 outpatient consultation sessions. Sessions with cVRE patients had higher rates of contamination of the environment (chair cultures were positive for VRE in 36% of outpatient consultation sessions, 58% of hemodialysis sessions; couch cultures were positive in 48% of outpatient consultation sessions, 42% of radiology sessions, and 45% of hemodialysis sessions), contamination of HCW gowns (gown cultures were positive in 20% of outpatient consultation sessions, 4% of radiology sessions, and 30% of hemodialysis sessions), and contamination of patients' own hands (hand cultures were positive in 36% of outpatient consultation sessions, 25% of radiology sessions, and 54% of hemodialysis sessions). Overall, contamination rates associated with pVRE patients attendance at outpatient consultations were 12% of those noted for cVRE patients (odds ratio, 0.10; 95% confidence interval, 0.03-0.42; P = .001). CONCLUSIONS: Given the nature of the contamination risk posed by fecally continent cVRE patients undergoing outpatient procedures, infection control measures should focus on effective HCW and patient hand hygiene and chair and couch cleaning, to minimize transmission of VRE.

Ambulatory Care↗

PubMed2000

Contaminated land liability issues: legal perspective.

Until recently, companies that contaminated land faced little prospect of being prosecuted or having claims made against them for any personal injuries or property damage arising from the contamination. Most companies would have considered it to be inconceivable that they could be required to clean up contamination resulting from an historic disposal, particularly if the disposal had been neither negligent nor unlawful. Current environmental law differs significantly, however, from the law which existed even 10 years ago. This paper examines liabilities arising from contaminated land. First, it discusses the new contaminated land regime and a parallel regime to remediate sites that are contaminated with radioactive substances. Second, it discusses remediation liabilities for water pollution. Such liabilities may well involve the remediation of contaminated land when groundwater is polluted. Finally, the paper examines liabilities for property damage and personal injuries arising from contamination by radioactive substances.

Environmental Pollution↗

PubMed2006

Tracking down human contamination in ancient human teeth.

DNA contamination arising from the manipulation of ancient calcified tissue samples is a poorly understood, yet fundamental, problem that affects the reliability of ancient DNA (aDNA) studies. We have typed the mitochondrial DNA hypervariable region I of the only 6 people involved in the excavation, washing, and subsequent anthropological and genetic study of 23 Neolithic remains excavated from Granollers (Barcelona, Spain) and searched for their presence among the 572 clones generated during the aDNA analyses of teeth from these samples. Of the cloned sequences, 17.13% could be unambiguously identified as contaminants, with those derived from the people involved in the retrieval and washing of the remains present in higher frequencies than those of the anthropologist and genetic researchers. This finding confirms, for the first time, previous hypotheses that teeth samples are most susceptible to contamination at their initial excavation. More worrying, the cloned contaminant sequences exhibit substitutions that can be attributed to DNA damage after the contamination event, and we demonstrate that the level of such damage increases with time: contaminants that are >10 years old have approximately 5 times more damage than those that are recent. Furthermore, we demonstrate that in this data set, the damage rate of the old contaminant sequences is indistinguishable from that of the endogenous DNA sequences. As such, the commonly used argument that miscoding lesions observed among cloned aDNA sequences can be used to support data authenticity is misleading in scenarios where the presence of old contaminant sequences is possible. We argue therefore that the typing of those involved in the manipulation of the ancient human specimens is critical in order to ensure that generated results are accurate.

DNA, Mitochondrial↗

PubMed1991

Environmental contamination in child day-care centers.

Enteropathogens associated with outbreaks of diarrhea in day-care centers are spread by the fecal-oral route through contaminated hands or environmental objects. This prospective study was undertaken to determine the prevalence of fecal coliform contamination in day care. Ten rooms in six centers housing 121 children less than 2 years of age were studied for 13 weeks (February to May 1988). Inanimate objects (n = 1,275), toy balls (n = 724), and hands (n = 954) were cultured 1-3 times per week. Fecal coliform contamination was common and was greater (p less than 0.05) for objects, toy balls, and hands of children in toddler compared with infant rooms. In five rooms in which clothes were worn over diapers, there was a significantly lower prevalence of fecal coliform contamination of toy balls (p less than 0.005), inanimate objects (p less than 0.05), and hands (p less than 0.001) when compared with rooms in which overclothes were not worn. Occurrence of diarrhea was significantly associated with increased contamination of hands (p = 0.001). Stool and environmental isolates from individual rooms had the same plasmid patterns, which were unique to each center. In summary, fecal coliform contamination of environmental objects and hands of children and caregivers in day-care centers is common; toy balls can serve as sentinels of contamination; fecal coliform contamination can be significantly decreased by use of overclothes; and Escherichia coli strains from stool showed the same plasmid patterns.

Child Day Care Centers↗

PubMed1993

Effect of fecal contamination on diarrheal illness rates in day-care centers.

Contact spread of enteropathogens in day-care centers is supported by the recovery (presence vs. absence) of fecal coliforms from hands and day-care center fomites. This prospective study was conducted to determine what, if any, quantitative measures of fecal coliforms predict the risk of diarrhea among day-care center attendees. Diarrheal illness without concomitant respiratory symptoms was monitored among 221 children aged < 3 years in 37 classrooms (24 day-care centers) through biweekly parental telephone interviews from October 1988 to May 1989 in Cumberland County, North Carolina. The risk of diarrhea was expressed as new episodes/classroom-fortnight. Contamination was expressed as the log10 fecal coliform count per unit of surface area, per toy, and per child and staff hands. Significant predictors of diarrheal risk were any hand contamination (p = 0.003) and the number of contaminated moist sites (hands, faucets, and sinks) (p = 0.006). After adjusting for the child/staff ratio using weighted multiple regression, the authors found that classrooms with either any hand contamination (p = 0.0015) or contamination on all moist sites (p = 0.015) had a significant twofold increased rate of diarrhea compared with classrooms without contamination. This was the first study to demonstrate an increased risk of diarrhea associated with fecal contamination and the frequent sink contamination in day-care centers.

Child Day Care Centers↗

PubMed2004

Small intestinal submucosa for vascular reconstruction in the presence of gastrointestinal contamination.

INTRODUCTION: Surgical options for vascular reconstruction in a contaminated field are limited and include prosthetic reconstruction or ligation with extra-anatomic bypass. With prosthetic insertion, rates of graft infection and failures (pseudoaneurysms and thrombosis) are high. In the emergent situations, extra-anatomic bypass is time-consuming and complex, and it produces marginal long-term results. Small intestinal submucosa (SIS) is a cell-free collagen matrix derived from porcine small intestine. Preliminary studies have demonstrated its ability to be remodeled into host tissue. In this study, we compared SIS to polytetrafluoroethylene (PTFE) as a vascular patch for arterial repair in the presence of massive gastrointestinal contamination to evaluate graft patency, incorporation, infection, and aneurysm formation. METHODS: Adult mongrel pigs underwent general anesthesia with Isoflurane and were then randomized to 1 of 3 groups: control, contamination (colon puncture with stool contamination of the pelvis), or shock + contamination (40% blood volume for 1 hour, then resuscitation with shed blood and crystalloid, plus contamination). All groups then underwent a left common iliac arteriotomy and further randomized to a 1 x 3-cm patch angioplasty with either SIS or PTFE. All received cefotetan for 24 hours. All animals were sacrificed between 2 and 4 weeks, and necropsy was performed. Grafts were cultured, and microscopic analysis with hematoxylin and eosin and trichrome was performed. Outcomes included pulse quality (normal or diminished) compared with opposite side, graft infection, and pseudoaneurysm; all were determined by a blinded investigator. RESULTS: Forty animals were randomized, and 1 died of abdominal sepsis. All control animals had normal distal pulses, no pseudoaneurysms, and no patch infections. The pseudoaneurysm rate for the contaminated PTFE patches was 25% compared with 0% in the SIS group (P = 0.09). Patch infection occurred in 73% of all PTFE patches compared with 8% of SIS patches (P < 0.03). Organisms present in the infected grafts included Escherichia coli, Bacteroides species, and other Gram-negative enterics. Histopathology demonstrated the presence of neointima in both SIS and PTFE. Only SIS was completely incorporated, with infiltration of collagen fibrils and lymphocytes. CONCLUSIONS: SIS was associated with improved graft patency, less infection, complete incorporation, and no false aneurysm formation when compared with PTFE. This may be due to its ability to provide a durable scaffold for cellularization and tissue remodeling. This material may offer a superior alternative to more complex vascular reconstruction techniques in contaminated fields.

Animals↗

PubMed1989

Microbial contamination of cosmetics and personal care items in Egypt--eye shadows, mascaras and face creams.

We examined a total of 150 samples, including 27 eye shadows, 27 mascaras and 96 face creams, for their microbial contents. Mascaras were generally more contaminated than eye shadows. More than 75% of the examined eye shadows contained fewer than 100 c.f.u./g aerobic bacterial count compared to 63% of the mascaras examined. Viable bacteria were not recovered from 61% and 48% of the eye shadows and mascaras respectively. While 4% of the eye shadows were heavily contaminated (contained more than 10(4) c.f.u./g), 15% of the mascaras were as heavily contaminated (with more than 10(4) c.f.u./ml of bacteria). Face creams were generally more heavily contaminated than eye shadows and mascaras. More than 70% of the examined creams contained more than 100 c.f.u./g of bacteria compared to 23% and 37% of eye shadows and mascaras respectively. Only 5% of the face creams were heavily contaminated. However, 27% of the creams were contaminated with more than 10(3)-10(4) c.f.u./g of bacteria compared to none in this range for both eye shadows and mascaras. Qualitative tests for detection of hazardous bacteria showed that none of the eye shadows were contaminated with any of those micro-organisms. Out of nine items of a specific brand of mascara, three isolates of Pseudomonas aeruginosa, one isolate of Citrobacter freundii and one isolate of Klebsiella pneumonia were detected. Among the creams, two brands showed the highest contamination levels with more than 85% of the tested samples containing more than 10(3) c.f.u./g fungi and at least 10(4) c.f.u./g bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗

PubMed1994

Probabilistic health risk assessment for exposures to estuary sediments and biota contaminated with polychlorinated biphenyls, polychlorinated terphenyls and other toxic substances.

A Latin Hypercube probabilistic risk assessment methodology was employed in the assessment of health risks associated with exposures to contaminated sediment and biota in an estuary in the Tidewater region of Virginia. The primary contaminants were polychlorinated biphenyls (PCBs), polychlorinated terphenyls (PCTs), polynuclear aromatic hydrocarbons (PAHs), and metals released into the estuary from a storm sewer system. The exposure pathways associated with the highest contaminant intake and risks were dermal contact with contaminated sediment and ingestion of contaminated aquatic and terrestrial biota from the contaminated area. As expected, all of the output probability distributions of risk were highly skewed, and the ratios of the expected value (mean) to median risk estimates ranged from 1.4 to 14.8 for the various exposed populations. The 99th percentile risk estimates were as much as two orders of magnitude above the mean risk estimates. For the sediment exposure pathways, the stability of the median risk estimates was found to be much greater than the stability of the expected value risk estimates. The interrun variability in the median risk estimate was found to be +/- 1.9% at 3000 iterations. The interrun stability of the mean risk estimates was found to be approximately equal to that of the 95th percentile estimates at any number of iterations. The variation in neither contaminant concentrations nor any other single input variable contributed disproportionately to the overall simulation variance. The inclusion or exclusion of spatial correlations among contaminant concentrations in the simulation model did not significantly effect either the magnitude or the variance of the simulation risk estimates for sediment exposures.

Adult↗

PubMed2004

Surface dust contamination and perceived indoor environment in office buildings.

UNLABELLED: The purpose of the study was to evaluate the impact of cleaning on indoor environment quality. Surface dust contamination and occupants' perception of the work environment factors and symptoms were the parameters studied. Six multi-floor office buildings were selected. Dust contamination on surfaces was sampled with gelatine foils and quantified using a BM-Dustdetector. Occupants' perceptions of the environment were assessed with modified MM-40 questionnaires. The results indicated that each building had its own surface dust contamination profile. Weekly cleaning maintained the surface dust contamination at the highest acceptable level for indoor environments. The occupants and their activities have a major effect on the level of dust particle contamination on desks. The correlation between the perceived surface dust contamination and the level of satisfaction with cleaning was as expected. Furthermore, surface dust contamination appeared not to be associated with work-related symptoms. PRACTICAL IMPLICATIONS: The results provide information about current program for contractors and clients, e.g. appropriate cleaning intervals of different surfaces, and the influence of disorder on result. After the evaluation of surface dust contamination levels, it will be possible for cleaning companies to focus on the most important surfaces to clean in order to enhance the quality of the indoor environment in office buildings. This should lead to future development work, which will require cooperation between contractors, clients, and research scientists. In office environments where high cleanliness is required, objective measurements (with instruments) are needed in addition to subjective measurements (the perceptions of occupants). It is essential to evaluate the efficiency of cleaning programs regularly with effective and appropriate quality-monitoring methods.

Analysis of Variance↗

PubMed2005

Removal of contaminants released from room surfaces by displacement and mixing ventilation: modeling and validation.

UNLABELLED: This paper presents the experimental and numerical modeling of contaminant dispersion in a full-scale environmental chamber with different room air distribution systems. For the experimental modeling, an area source with uniform emissions of a hypothetical contaminant (SF6) from the entire floor surface is designed and constructed. Two different types of ventilation are studied: displacement and mixing ventilation. A computer model for predicting the contaminant dispersion in indoor spaces was validated with experimental data. The validated model is used to study the effects of airflow and the area-source location on contaminant dispersion. Results show that the global airflow pattern has a strong impact on the distribution of the contaminants. In general, the personal exposure could be estimated by analyzing the relative source positions in the airflow pattern. Accordingly, the location of an exhaust diffuser may not greatly affect the airflow pattern, but can significantly affect the exposure level in the room. PRACTICAL IMPLICATIONS: When designing ventilation in addition to bringing fresh air to occupants, it is important to consider the removal of contaminants released in the off-gassing of building materials. Typical indoor off-gassing examples are emissions of volatile organic compounds from building enclosure surfaces such as flooring and painted walls. In this study, we conducted experimental and numerical modeling of different area sources in a mock-up office setup, with displacement or mixing ventilation. Displacement ventilation was as successful as mixing ventilation in removing the contaminant source from the floor area. Actually, the most important consideration in the removal of these contaminants is the relative position of the area source to the main airflow pattern and the occupied zone.

Air Pollutants↗

PubMed1998

Electron contamination in 8 and 18 MV photon beams.

The contribution from contaminant electrons in the buildup region of a photon beam must be separated when calculating the dose using a photon convolution kernel. Their contribution can be extrapolated from fractional depth dose (FDD) data using the fractional depth kerma (or the "equilibrium dose") derived from measured quantities such as beam attenuation with depth, phantom scatter factor as a function of field size and depth, and inverse-square law for the incident photon beam. Good agreement is observed between the extrapolated and the EGS4 Monte Carlo simulated, primary dose-to-kerma ratios in the surface region for the photon beams, excluding electron contamination. The FDD was measured using a Scanditronix photon diode and was normalized to a reference depth far beyond maximum range of contaminant electrons. An analysis for the 8 and 18 MV photon beams from a Varian 2100CD indicates that at a source-to-surface distance (SSD) of 100 cm, the maximum electron contaminant dose (relative to its maximum FDD) varies from 1% to 33% for 8 MV and 2% to 44% for 18 MV, for square collimator settings ranging from 5 to 40 cm (defined at 100 cm from the source). This value at a depth of maximum dose (2 cm for 8 MV and 3.5 cm for 18 MV) can reach 1% for 8 MV and 2.3% for 18 MV. This contaminant electron dose is almost independent of SSD for 8 MV and starts to fall off for 18 MV at SSDs larger than 120 cm. Compared with the open beam, the contaminant electron dose increases when a solid tray is used, and the magnitude of increase increases with field size, reaching 19% and 16% for a 40 x 40 cm2 field for 8 and 18 MV photons, respectively. The contaminant electron dose increases slightly for a blocked beam compared with an open beam of the same field size if a tray is used in both cases. The contaminant electron dose for the wedged field is less than that for an open field. However, the reduction is less significant at larger collimator settings (c = 20 cm) and may increase slightly for 8 MV photons.

Electrons↗