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PubMed1978

Pontiac fever. An epidemic of unknown etiology in a health department: I. Clinical and epidemiologic aspects.

In July 1968, an explosive epidemic of acute febrile illness occurred at a county health department facility in Pontiac, Michigan. Illness characterized principally by fever, headache, myalgia, and malaise affected at least 144 persons, including 95 of 100 persons employed in the health department building. The mean incubation period was approximately 36 hours. Illness was self-limited, generally lasting from two to five days. Secondary cases did not occur in family contacts and second attacks did not consistently follow re-exposure in the building. A defective air-conditioning system was implicated as the source and mechanism of spread of the causative factor. However, extensive laboratory and environmental investigations failed to identify the etiologic agent. Since these investigations a bacterium similar to or identical with the agent responsible for Legionnaires' Disease has been isolated from guinea pigs exposed to the Pontiac health department building in 1968 as well as from guinea pigs exposed to water from the evaporative condenser. Paired sera from 32 cases of Pontiac Fever showed seroconversion or diagnostic rises in antibody titers to this bacterium.

Acute Disease↗
PubMed1986

Outbreak of Legionnaires' disease in Glasgow Royal Infirmary: microbiological aspects.

The bacteriological investigation of an outbreak of Legionnaires' disease in Glasgow Royal Infirmary affecting 16 patients is described. Most of the patients had been treated in high-dependency areas on two floors of the hospital supplied by the same two air-conditioned ventilation systems. The source of infection was traced to contamination of a cooling tower from which a plume of spray discharged into the intake vents of the two ventilation systems. Rubber grommets within the cooling tower probably provided a nidus of infection there. The control and management of the outbreak are discussed: a policy of frankness about the course and progress of the investigations was adopted and helped to allay anxiety on the part of both staff and media.

Air Conditioning↗
PubMed1998

Risk factors for near-fatal asthma. A case-control study in hospitalized patients with asthma.

We prospectively recruited patients admitted to the hospital with severe asthma to comprehensively evaluate the association of historical and physiologic features with the risk of near-fatal asthma (NFA). A case-control study design was used. All patients admitted with NFA (cases) were identified prospectively and compared with asthma patients admitted during the same period without respiratory failure (controls). Nineteen cases (age: 40.2 +/- 12.0 yr) (mean +/- SD) and 80 controls (age: 36 +/- 13.5 yr) were enrolled. Duration of asthma, gender, smoking status, ethnicity, and prevalence of atopy were similar in the case and control groups. More than 80% of patients in both groups reported worsening symptoms for more than 48 h before admission, and more than 50% were worse for longer than 7 d. There was no difference in degree of airways obstruction or bronchial hyperresponsiveness (PC20). Perception of dyspnea was similar in the cases and controls, but among cases the males had greater impairment than the females (Borg score: 1.9 +/- 1. 4 versus 3.9 +/- 1.2: p = 0.05). Univariate analysis identified a history of previous mechanical ventilation (OR: 27.5; 95% CI: 6.60 to 113.7), admission to the intensive care unit (ICU) (OR: 9.9; 95% CI: 3.0 to 32.9), history of worse asthma during January and February (OR: 3.5; 95% CI: 1.0 to 11.8), and use of air-conditioning (OR: 15.0; 95% CI: 1.3 to 166) as risk factors for NFA. Of concern was the dependence of most patients (59.8%) on the emergency department (ED) for initial care, and the small number of cases (16%) in which patients visited a physician before admission to the hospital. We have confirmed risk factors identified previously in retrospective studies of fatal and NFA, and have also shown that hospitalized patients with asthma, irrespective of severity of their asthma, share several characteristics, especially in terms of their failure to respond to worsening asthma.

Acute Disease↗
PubMed1975

Heat wave mortality in New York City, 1949 to 1970.

Epidemiological studies have been carried out to search for an influence of air conditioning on patterns of heat wave mortality in New York City. Two models were used to predict total daily summer mortality as a function of temperature; one of the models included heat acclimatization effects. Ratios of the models' predictions of heat wave mortality to actual mortality were calculated for heat waves occurring during 12 summers in the period 1949 to 1970. Trends in these ratios as a function of time were sought. The analysis suggests that the relative magnitudes of excess mortality during initial summer heat waves may have decreased over the 21-year period. No trend was observed for excess mortality during late summer heat waves.

Acclimatization↗
PubMed1996

[Results of continuous gas measurements rabbit housing by using multi-gas monitoring].

Investigations of slatted floor keeping of rabbits in an air conditioned chamber with multigas monitoring over a period of more than two month have shown that the average values per week were on a low level between 575 and 685 ppm (carbon dioxide), 3.4 and 5.6 ppm (ammonia) resp. Concentration of ammonia reached in maximum 12.3 ppm for a short time. Nitrous oxide concentration was measured on a global value (253 up to 317 ppb). A slight tendency of increasing CO2 and NH3 values with the begin of light period--obviously related to increased locomotoric activity--approximately was observed. In slatted floor keeping calculated emission of ammonia was very low (0.23 gram per 500 kg an hour).

Air Conditioning↗
PubMed1981

Isolation of Legionella pneumophila from water systems: methods and preliminary results.

A preliminary survey of water systems in hospitals and hotels showed that Legionella pneumophila may be found in water storage and distribution systems as well as in the recirculating cooling water of air-conditioning plants. Altogether 42 isolates of L pneumophila were made from 31 establishments, six of which were associated with cases of legionnaires' disease but in 25 of which there was no known association with disease. In the six establishments implicated epidemiologically as the source of legionnaires' disease, these organisms were found in each of their water-distribution systems and also in the cooling water from each of the three with cooling towers. In establishments not associated with cases, water from three out of nine cooling towers, four out of 24 taps or showers, and one out of 15 storage tanks was found to contain legionellae. The organisms were isolated by guinea-pig inoculation and subsequent culture of their peritoneal fluid, liver, and spleen. Finding L pneumophila in water systems in the absence of cases of legionnaires' disease should not at present be an indication for attempts at eradication.

Air Conditioning↗
PubMed1992

Symptomatic La Crosse virus infections of the central nervous system: a study of risk factors in an endemic area.

In most years, La Crosse virus is the most common cause of reported mosquito-borne illness in the United States. The authors conducted a case-control study to determine if behavioral and environmental factors influenced the risk of La Crosse virus illness. Data were gathered on 31 serologically confirmed cases and 60 age-, sex-, and geography-matched controls in West Virginia in 1987 and 1988. Univariate analysis revealed minimal elevation of disease risk (odds ratios (ORs) less than 2.0) with increased time outdoors, non-use of insect repellent, non-use of air conditioning, lack of screened windows, and not wearing protective clothing. Univariate and multivariate analysis indicated that the presence of tree holes significantly increased disease risk (OR = 8.5 for greater than or equal to 1 tree hole vs. 0 tree holes). The following factors may also increase disease risk, although the findings were not statistically significant: discarded tires (OR = 3.2 for greater than or equal to 10 tires vs. 0-9 tires); non-tire artificial containers (OR = 4.1 for greater than or equal to 6 containers vs. 0-5 containers); and close proximity of the house to the forest edge (OR = 3.2 for 0-49 ft (0-14.9 m) vs. greater than or equal to 50 ft (greater than or equal to 14.9 m)). The authors conclude that the presence of natural breeding sites (tree holes) is an important risk factor for La Crosse virus illness. These results may be important in guiding future efforts aimed at preventing infection with La Crosse virus.

Adolescent↗
PubMed1981

Bacterial fouling of a hospital closed-loop cooling system by Pseudomonas sp.

During the summer of 1979 the air-conditioning system at a hospital in Boston deteriorated, and this led to total failure of some chilling units. Patient care and operating-room areas were affected. Investigation of the problem ruled out mechanical and electrical causes, but revealed a strain of Pseudomonas sp. biofouling heat transfer tubes of the closed chilled water system. The pseudomonads apparently were stimulated to grow by low concentrations of ethylene glycol antifreeze. The proximate source of these organisms was an expansion tank located in a 33 degrees C environment. The organisms probably originated from the potable water supply of the hospital. Fouling was eventually cleaned by prolonged and expensive treatments of the closed chilled water system. Pseudomonas sp. is frequently isolated from hospital-acquired infections at our institution (Beth Israel Hospital, Boston, Mass.); however, our studies with fluorescent dye tracers indicated that organisms were prohibited from entering patient areas via contaminated water from the chillers. Microbiologists must become cognizant of seemingly unimportant microbial environments within hospitals that may indirectly contribute to hospital-acquired infections.

Air Conditioning↗
PubMedDate not supplied

Cooling towers--a potential environmental source of slow-growing mycobacterial species.

Over the last decade a rise in the frequency of disease caused by nontuberculous mycobacteria (NTM) has occurred, especially among AIDS patients. The lack of evidence for person-to-person transmission indicates the environment is a source of infection. The ecology and environmental sources of NTMs are poorly understood, and many pathogenic strains have not been observed outside of clinical cases. Several species of NTMs have been reported from treated water distribution systems; however, one type of manmade environment that has not been examined for mycobacteria is that of cooling towers of air-conditioning systems. Such environments not only harbor a variety of microbial species, they also disseminate them in aerosols. The present investigation examined nine cooling towers from various locations in the United States. Cooling tower water was concentrated, treated with cetylpyridinium chloride, and plated onto Middlebrook 7H10 agar supplemented with OADC and cycloheximide. Colonies presumed to be mycobacterial species were isolated and acid-fast stained. Identification was made by amplifying and sequencing 1450 bp fragments of the 16S rRNA gene in both directions, and comparing resulting sequences with those in GenBank. Results showed that at least 75% of tower samples contained NTMs, and most of the isolates closely matched known mycobacterial pathogens. Isolates most closely matched the following GenBank sequences: Mycobacterium intracellulare, M. szulgai, M. bohemicum, M. gordonae, M. nonchromogenicum, and M. n. sp. "Fuerth 1999." This is the first report of specific NTMs in cooling tower water, and the first report of M. n. sp. "Fuerth 1999" from any environmental sample. Although cooling towers have a relatively high pH, they may favor the growth and dissemination of such potential pathogens, and future epidemiologic investigations should consider cooling towers as possible environmental sources of mycobacteria.

Air Conditioning↗
PubMed1993

Stimulatory effect of cooling tower biocides on amoebae.

Two species of amoebae were isolated from the cooling tower of an air-conditioning system and examined for effects of exposure to four cooling tower biocides, a thiocarbamate compound, tributyltin neodecanoate mixed with quaternary ammonium compounds, another quaternary ammonium compound alone, and an isothiazolin derivative. The amoebae isolated were Acanthamoeba hatchetti and a Cochliopodium species. Two other amoeba cultures, an A. hatchetti culture and Cochliopodium bilimbosum, were obtained from the American Type Culture Collection (ATCC) and were also tested. The cooling tower isolates were more resistant to most of the biocides than the ATCC isolates were. The isothiazolin derivative was the least inhibitory to all four amoeba isolates, and tributyltin neodecanoate mixed with quaternary ammonium compounds was the most inhibitory to three of the four isolates. After exposure to lower concentrations of the biocides, including for one strain the manufacturer's recommended concentration of one biocide, the cooling tower amoeba populations increased significantly compared with unexposed controls, whereas the ATCC isolates were not stimulated at any of the concentrations tested. In some cases, concentrations which stimulated cooling tower amoebae inhibited the growth of the ATCC isolates. These results suggest that cooling tower amoebae may adapt to biocides, underscoring the need to use freshly isolated cooling tower organisms rather than organisms from culture collections for testing the efficacy of such biocides. The stimulatory effect of biocides on amoeba populations is an alarming observation, since these organisms may be reservoirs for legionellae. Biocides used to control microbial growth may actually enhance populations of host organisms for pathogenic bacteria.

Acanthamoeba↗
PubMed2006

Prevalence study of Legionella spp. contamination in ferries and cruise ships.

BACKGROUND: In the last years, international traffic volume has significantly increased, raising the risk for acquisition of infectious diseases. Among travel-associated infections, increased incidence of legionellosis has been reported among travellers. Aim of our study was: to describe the frequency and severity of Legionella spp. contamination in ferries and cruise ships; to compare the levels of contamination with those indicated by the Italian ministerial guidelines for control and prevention of legionellosis, in order to assess health risks and to adopt control measures. METHOD: A prevalence study was carried out on 9 ships docked at the seaports of northern Sardinia in 2004. Water samples were collected from critical sites: passenger cabins, crew cabins, kitchens, coffee bars, rooms of the central air conditioning system. It was performed a qualitative and quantitative identification of Legionella spp. and a chemical, physical and bacteriological analysis of water samples. RESULTS: Forty-two percent (38/90) water samples were contaminated by Legionella spp.. Positive samples were mainly drawn from showers (24/44), washbasins (10/22). L. pneumophila was isolated in 42/44 samples (95.5%), followed by L. micdadei (4.5%). Strains were identified as L. pneumophila serogroup 6 (45.2%; 19 samples), 2-14 (42.9%), 5 (7.1%) and 3 (4.8%). Legionella spp. load was high; 77.8% of the water samples contained > 10(4) CFU/L. Low residual free chlorine concentration (0-0.2 mg/L) was associated to a contamination of the 50% of the water samples. CONCLUSION: Legionella is an ubiquitous bacterium that could create problems for public health. We identified Legionella spp. in 6/7 ferries. Microbial load was predominantly high (> 10(4) CFU/L or ranging from 10(3) to 10(4) CFU/L). It is matter of concern when passengers are subjects at risk because of Legionella spp. is an opportunist that can survive in freshwater systems; high bacterial load might be an important variable related to disease's occurrence. High level of contamination required disinfecting measures, but does not lead to a definitive solution to the problem. Therefore, it is important to identify a person responsible for health safety in order to control the risk from exposure and to apply preventive measures, according to European and Italian guidelines.

Air Conditioning↗
PubMed1986

Immunologic response to aerosols of affinity-purified antigen in hypersensitivity pneumonitis.

On epidemiologic grounds, respirable particles from chilled-water air-conditioning systems in textile production plants have been implicated as a cause of hypersensitivity pneumonitis. We have purified the antigen from scum growing in this chilled water by antibody-affinity chromatography by use of IgG isolated from a pool of serum obtained from three workers with disease. Two patients with the disease, three coworkers without the disease, and two unexposed control subjects inhaled a dose of the purified antigen approximately equivalent to that amount calculated to be inhaled during an 8-hour work shift. Both workers with disease experienced fever, malaise, cough, and dyspnea 6 to 8 hours after the aerosol challenge. In these two patients the exposure evoked a transient decrease in circulating lymphocytes, predominantly T cells. Before challenge the patients' peripheral blood mononuclear cells demonstrated a blastogenic response to the antigen. The responding cells had disappeared from the circulation 24 hours after the challenge. Seventy-two hours after the challenge, mononuclear cells that were producing large amounts of specific IgG antibody appeared in the circulation. We conclude that the same antigen(s) that react with IgG antibody produced an acute episode of the disease, that specific antigen-recognition cells disappear from the peripheral blood after exposure to the antigen (presumably because they are attracted to the lung), and that antibody-forming cells appear in the peripheral blood approximately 2 days after a challenge. These antigen-specific reactions of circulating mononuclear cells may be specific for the disease, but studies on a larger number of cases are needed to be certain.

Aerosols↗
PubMed2004

Thermal comfort in practice.

UNLABELLED: Since the early twentieth century when air-conditioning began penetrating the market in a serious way, there has been a need for human factors research upon which HVAC engineering practice could be based. Now we have nearly a century of thermal comfort research from climate chambers and much has been learnt in that time. By stripping the research problem back to essential cause-and-effect variables, climate chamber methods have delivered results that are amenable to rigorous data analyses leading to unequivocal conclusions. However, in the minds of HVAC practitioners there are persistent doubts about the experiential realism of the chamber methodology, and the external validity of their findings, in particular, their relevance to building occupants going about their normal daily routines in fully-engineered indoor climatic environments. In response to this methodological concern in the 1990s, ASHRAE commissioned a series of thermal comfort studies aimed at field validating the findings of climate chamber research and the HVAC standards based upon them in a variety of climatic contexts around the world. This paper discusses the methodological benefits and constraints of conventional climate chamber research in comparison to the field-based alternative. In particular, issues such as sample size and demographics, research design, instrumentation and indoor climatic measurement procedures, questionnaires, clothing insulation and metabolic rate assessment techniques are analyzed. The discussion of methodology is then extended to the discipline of environmental psychology, which should have made a much more significant contribution to the topic of thermal comfort, and yet has remained relatively silent. The paper finishes by considering why engineers, most notably P.O. Fanger, have come to dominate a research topic that falls so clearly within the scope of psychology. HVAC engineering is the profession most directly occupied in the practice of thermal comfort, and therefore an engineer such as Fanger has been ideally qualified to design and conduct research, and even more important, presents its results in a way most directly useful to thermal comfort practitioners. PRACTICAL IMPLICATIONS: The paper gives practical advice on evaluating and designing for thermal comfort.

Air Conditioning↗
PubMedDate not supplied

The relationships between personal PM exposures for elderly populations and indoor and outdoor concentrations for three retirement center scenarios.

Personal exposures, indoor and outdoor concentrations, and questionnaire data were collected in three retirement center settings, supporting broader particulate matter (PM)--health studies of elderly populations. The studies varied geographically and temporally, with populations studied in Baltimore, MD in the summer of 1998, and Fresno, CA in the winter and spring of 1999. The sequential nature of the studies and the relatively rapid review of the mass concentration data after each segment provided the opportunity to modify the experimental designs, including the information collected from activity diary and baseline questionnaires and influencing factors (e.g., heating, ventilation, and air-conditioning (HVAC) system operation, door and window openings, air exchange rate) measurements. This paper highlights both PM2.5 and PM10 personal exposure data and interrelationships across the three retirement center settings, and identifies the most probable influencing factors. The current limited availability of questionnaire results, and chemical speciation data beyond mass concentration for these studies, provided only limited capability to estimate personal exposures from models and apportion the personal exposure collections to their sources. The mean personal PM2.5 exposures for the elderly in three retirement centers were found to be consistently higher than the paired apartment concentrations by 50% to 68%, even though different facility types and geographic locations were represented. Mean personal-to-outdoor ratios were found to 0.70, 0.82, and 1.10, and appeared to be influenced by the time doors and windows were open and aggressive particle removal by the HVAC systems. Essentially identical computed mean PM2.5 personal clouds of 3 micrograms/m3 were determined for two of the studies. The proposed significant contributing factors to these personal clouds were resuspended particles from carpeting, collection of body dander and clothing fibers, personal proximity to open doors and windows, and elevated PM levels in nonapartment indoor microenvironments.

Aerosols↗
PubMed1997

Effect of drying conditions on the taxane content of the needles of ornamental Taxus.

The effect of drying intact clippings of Taxus on the recovery of taxol and related compounds was studied under different drying conditions which included tobacco drying barn, greenhouse, shadehouse, air conditioned laboratory, oven, and freeze-drying. For clippings dried under tobacco barn, greenhouse, oven, and freeze-drying conditions, nearly total recovery of the expected levels based upon projections from analysis of fresh biomass was observed for taxol and cephalomannine. However, only 75-80% of the expected values for 10-deacetyltaxol and 10-deacetylbaccatin III were found. When the length of drying was extended up to 10 and 15 days as in the shadehouse and laboratory conditions, the recovery of all taxanes was adversely affected.

Alkaloids↗
PubMed1986

Finite difference analysis of respiratory heat transfer.

A numerical computer model of heat and water transfer within the tracheobronchial tree of humans was developed based on an integral formulation of the first law of thermodynamics. Simulation results were compared with directly measured intraluminal airway temperature profiles previously obtained in normal human subjects, and a good correlation was demonstrated. The model was used to study aspects of regional pulmonary heat transfer and to predict the outcomes of experiments not yet performed. The results of these simulations show that a decrease in inspired air temperature and water content at fixed minute ventilation produces a proportionately larger increase in heat loss from extrathoracic airways relative to intrathoracic, whereas an increase in minute ventilation at fixed inspired air conditions produces the opposite pattern, with cold dry air penetrating further into the lung, and that changes in breathing pattern (tidal volume and frequency) at fixed minute ventilation and fixed inspiratory-to-expiratory (I/E) ratio do not affect local air temperature profiles and heat loss, whereas changes in I/E ratio at fixed minute ventilation do cause a significant change.

Asthma↗
PubMed2005

Combined effect of carvacrol and packaging conditions on radiosensitivity of Escherichia coli and Salmonella Typhi in ground beef.

This study was undertaken to evaluate the effect of 1.0% carvacrol and 0.1% tetrasodium pyrophosphate on the radiation D10 of Escherichia coli and Salmonella Typhi added to ground beef at a concentration of 10(5) CFU/g. The ground beef was then packaged under four different atmosphere conditions: air (78.1% N2, 20.9% O2, 0.036% CO2), 100% CO2, modified atmosphere (60% O2, 30% CO2, 10% N2) and vacuum. Samples were irradiated at doses of 0.1 to 0.6 kGy for E. coli and 0.5 to 2.0 kGy for Salmonella Typhi. Radiation D10-values of 0.126 and 0.526 kGy were observed for E. coli and Salmonella Typhi, respectively, when meat was packed under air. When meat was packed under modified atmosphere conditions, the radiation D10-values for E. coli and Salmonella Typhi were 0.086 and 0.221 kGy, respectively. The addition of carvacrol and tetrasodium pyrophosphate and the use of modified atmosphere packaging reduced the radiation D10-value from 0.126 to 0.046 kGy for E. coli and from 0.526 to 0.053 kGy for Salmonella Typhi. Under vacuum and 100% CO2 conditions, the radiation D10 reduction was not as great as that for the modified atmosphere regardless of the presence or absence of carvacrol and tetrasodium pyrophosphate.

Animals↗