Germicidal ultraviolet irradiation in air conditioning systems: effect on office worker health and wellbeing: a pilot study

Effectiveness of filtering or decontaminating air to reduce or prevent respiratory infections: A systematic review

Installation of technologies to remove or deactivate respiratory pathogens from indoor air is a plausible non-pharmaceutical infectious disease control strategy.

OBJECTIVE

We undertook a systematic review of worldwide observational and experimental studies, published 1970-2022, to synthesise evidence about the effectiveness of suitable indoor air treatment technologies to prevent respiratory or gastrointestinal infections.

METHODS

We searched for data about infection and symptom outcomes for persons who spent minimum 20 h/week in shared indoor spaces subjected to air treatment strategies hypothesised to change risk of respiratory or gastrointestinal infections or symptoms.

RESULTS

Pooled data from 32 included studies suggested no net benefits of air treatment technologies for symptom severity or symptom presence, in absence of confirmed infection. Infection incidence was lower in three cohort studies for persons exposed to high efficiency particulate air filtration (RR 0.4, 95%CI 0.28-0.58, p < 0.001) and in one cohort study that combined ionisers with electrostatic nano filtration (RR 0.08, 95%CI 0.01-0.60, p = 0.01); other types of air treatment technologies and air treatment in other study designs were not strongly linked to fewer infections. The infection outcome data exhibited strong publication bias.

CONCLUSIONS

Although environmental and surface samples are reduced after air treatment by several air treatment strategies, especially germicidal lights and high efficiency particulate air filtration, robust evidence has yet to emerge that these technologies are effective at reducing respiratory or gastrointestinal infections in real world settings. Data from several randomised trials have yet to report and will be welcome to the evidence base.

An Emphasis on Engineering Controls and Administrative Controls in the Prevention and Control of COVID-19 in an Orthodontic Setting: Thinking Beyond Tomorrow

Introduction: Most of the initial focus in handling COVID-19 had been based on avoiding exposure by refraining from rendering most treatments other than those considered an emergency or urgent. Post-lockdown, with the resumption of most activities, there has been concern over the possibility of transmission scenarios if sufficient care is not taken. The control and prevention of the spread of infections when elimination of exposure is not possible is chiefly achieved through the judicious use of engineering controls and administrative controls in a clinical setting in addition to the standard protocols and transmission-based protocols. True safety lies in being one step ahead. There have been mentions of the possibility that COVID-19 could be opportunistic airborne in its spread, in addition to being spread via saliva, droplets, and contaminated surfaces or objects.

Method: A literature search of PubMed, Google Scholar, Cochrane Library, and advisories released by such organizations as the World Health Organization (WHO), Centers for Disease Control and Prevention (CDC), Ministry of Health and Family Welfare (MOFHW), European Centre for Disease Prevention and Control (ECDC), Chinese Center for Disease Control and Prevention (China CDC), American Dental Association (ADA), Canadian Dental Association (CDA), French National Dentists Association, Dental Council of Belgium, National Health Service, England (NHS UK), National Health Service Scotland (NHS Scotland), and International Society for Infectious Diseases (ISID) was performed, with search parameters aimed at gathering information pertaining to infection control and cross infection control in dental settings as related to orthodontics.

Result: There have been numerous articles and advisories published over the last 20 years, but the main focus has been on safe practices and to an extent on personal protective equipment, with relatively less emphasis on the need for respiratory protection by way of engineering controls and administrative controls. This review highlights the engineering and administrative controls that can be put into effect to make infection control and prevention much more effective.

Conclusion: Any health care facility must be able to prevent, contain, and control infections with no risk of nosocomial infections. For this, an assumption has to be made that every individual in a health care setting is either at risk or a risk, depending on whether the person is infected or not. Meticulous attention to stringent policies of hygiene and infection control and prevention, coupled with suitable supporting engineering and administrative controls, is to be made a standard way of life in such facilities.

The antimicrobial efficacy of shielded ultraviolet germicidal irradiation in CT rooms with intense human circulation

PURPOSE

Computed tomography (CT) premises are one of the strategic points in the spread of hospital-acquired infections. Ultraviolet germicidal irradiation (UVGI) is an effective method that could potentially be used to purify the ambient air in them. However, it cannot be directly used in the presence of humans and, therefore, it is not operationally suitable in such units with continuous human circulation. Newer devices have been developed to purify air with more efficient and shielded UV-C sources. This study aims to assess the microbial air contamination in CT scanning rooms and investigates the efficacy and technical considerations of shielded UV-C arrays.

METHODS

Two shielded UVGI systems, each equipped with 15 Watt UV-C LED arrays, were tested in a very busy CT unit. Initially, a pilot study was performed to determine ambient microorganisms under routine conditions before UVGI installation, followed by three basic scenarios of UVGI use under normal and abnormal conditions: A, UVGI, with both air-conditioning (AC) and ventilation on; B, UVGI, with AC on and ventilation off; C, UVGI, with both AC and ventilation off. Ambient air was sampled in various time points before and after the initialization of UV irradiation and analyzed for colony formation.

RESULTS

The mean total colony count in the pilot study was 1360±450 CFU/m3. Pre-UVGI colony count was 3510 CFU/m3 for Scenario A, ~10000 CFU/m3 for Scenario B and 990 CFU/m3 for Scenario C. Thirty minutes after UVGI, total colony counts in all three scenarios dropped to 30 to 70 CFU/m3. Under normal operating conditions and UVGI, the mean colony count was found as 21.4±13.5 CFU/m3 and the average efficacy of the UVGI was found as 99.39%.

CONCLUSION

This study identified substantial microbial air contamination in CT scanning rooms during normal and abnormal operating conditions. UV-C LED arrays effectively eliminate these microbiological contaminants. This effect is also observed under abnormal operating conditions where no other means of ventilation or air conditioning exists.

Lagrangian modeling of inactivation of airborne microorganisms by in-duct ultraviolet lamps

There has been increasing interest in modeling the UV inactivation on airborne microorganisms via the Lagrangian approach as a result of its outstanding features in calculating UV dose with particle trajectory. In this study, we applied the Lagrangian method to model the disinfection performance of in-duct UV lamps on three bacteria: Pseudomonas alcaligenes, Salmonella enterica and Escherichia coli, respectively. For modeling, the airborne bacteria's inactivation was determined by critical survival fraction probability (CSFP) and maximal bearable UV dose (MBUD) methods, respectively. The results indicated that Lagrangian modeling utilizing the MBUD method needs to appropriately evaluate the maximal UV dose (D _mb ), which is bearable for airborne microorganisms. The disinfection efficacy obtained by using the CSFP method agreed well with experimental measurements. Within the Lagrangian framework, the recommended empirical value for critical survival fraction (F _sc ) was 0.4 for modeling the disinfection efficacy of in-duct UV lamps. Besides, the disinfection efficacies of in-duct UV lamps with full luminous length on P. alcaligenes and E. coli were 100% with Re within the range of 4.11 × 10⁴ to 8.22 × 10⁴. Moreover, the present numerical model was also applied for further validation with inactivation measurements of in-duct UV lamps performed by the U.S. Environmental Protection Agency (EPA). Based on the results, the UV disinfection efficacies obtained by the present modeling method had a closed agreement with EPA experimental results. It deserved to pay more investigations on the optimal value of F _sc in further for accurately applying Lagrangian modeling on air UV disinfection.

The Discovery of an Unusual Cause of Indoor Radiation Pollution

The objective of our study is to investigate the reasons why 21 persons suffered erythema and other skin changes, and conjunctivae infection after staying in a closed room for three hours. A multi-disciplinary case study including interviews, building and ventilation inspections, was performed by a multidisciplinary team comprising a medical epidemiologist, and an industrial hygienist. A self-administered questionnaire was designed to determine the magnitude of the health problem of the affected students. By a process of investigative elimination, we deduced that the symptoms were caused by accidental exposure to ultraviolet C radiation where it was radiated from the germicidal ultraviolet lamps. The most common symptoms and signed presented were erythema of skin and conjunctivae infection. The erythema of skin and conjunctivae infection arose from exposure to ultraviolet C radiation and that safeguards are needed to ensure ultraviolet germicidal lamps are not accidentally switched on while a room is occupied.

Fungal pollution of indoor environments and its management

Indoor environments play important roles in human health. The health hazards posed by polluted indoor environments include allergy, infections and toxicity. Life style changes have resulted in a shift from open air environments to air tight, energy efficient, environments, in which people spend a substantial portion of their time. Most indoor air pollution comes from the hazardous non biological agents and biological agents. Fungi are ubiquitous in distribution and are a serious threat to public health in indoor environments. In this communication, we have reviewed the current status on biotic indoor air pollution, role of fungi as biological contaminants and their impact on human health.

Fungal pollution of indoor environments and its management

Indoor environments play important roles in human health. The health hazards posed by polluted indoor environments include allergy, infections and toxicity. Life style changes have resulted in a shift from open air environments to air tight, energy efficient, environments, in which people spend a substantial portion of their time. Most indoor air pollution comes from the hazardous non biological agents and biological agents. Fungi are ubiquitous in distribution and are a serious threat to public health in indoor environments. In this communication, we have reviewed the current status on biotic indoor air pollution, role of fungi as biological contaminants and their impact on human health.

Effect of temperature and relative humidity on ultraviolet (UV 254) inactivation of airborne porcine respiratory and reproductive syndrome virus

The objective of this research was to estimate the effects of temperature and relative humidity on the inactivation of airborne porcine reproductive and respiratory syndrome (PRRS) virus by ultraviolet light (UV₂₅₄). Aerosols of PRRS virus were exposed to one of four doses of UV₂₅₄ under nine combinations of temperature (n = 3) and relative humidity (n = 3). Inactivation constants (k), defined as the absolute value of the slope of the linear relationship between the survival fraction of the microbial population and the UV₂₅₄ exposure dose, were estimated using the random coefficient model. The associated UV₂₅₄ half-life dose for each combination of environmental factors was determined as (log₁₀ 2/k) and expressed as UV₂₅₄ mJ per unit volume. The effects of UV₂₅₄ dose, temperature, and relative humidity were all statistically significant, as were the interactions between UV₂₅₄ dose × temperature and UV₂₅₄ dose × relative humidity. PRRS virus was more susceptible to ultraviolet as temperature decreased; most susceptible to ultraviolet inactivation at relative humidity between 25% and 79%, less susceptible at relative humidity ≤24%, and least susceptible at ≥80% relative humidity. The current study allows for calculating the dose of UV₂₅₄ required to inactivate airborne PRRS virus under various laboratory and field conditions using the inactivation constants and UV₂₅₄ half-life doses reported therein.

Ultraviolet irradiation and the mechanisms underlying its inactivation of infectious agents

We review the principles of ultraviolet (UV) irradiation, the inactivation of infectious agents by UV, and current applications for the control of microorganisms. In particular, wavelengths between 200 and 280 nm (germicidal UV) affect the double-bond stability of adjacent carbon atoms in molecules including pyrimidines, purines and flavin. Thus, UV inactivation of microorganisms results from the formation of dimers in RNA (uracil and cytosine) and DNA (thymine and cytosine). The classic application of UV irradiation is the inactivation of microorganisms in biological safety cabinets. In the food-processing industry, germicidal UV irradiation has shown potential for the surface disinfection of fresh-cut fruit and vegetables. UV treatment of water (potable and wastewater) is increasingly common because the process is effective against a wide range of microorganisms, overdose is not possible, chemical residues or by-products are avoided, and water quality is unaffected. UV has been used to reduce the concentration of airborne microorganisms in limited studies, but the technology will require further development if it is to gain wider application. For bioaerosols, the primary technical challenge is delivery of sufficient UV irradiation to large volumes of air, but the absence of UV inactivation constants for airborne pathogens under a range of environmental conditions (temperature, relative humidity) further compounds the problem.

Sudden temperature changes and respiratory symptoms--an experimental approach

BACKGROUND

Exposure to air-conditioning systems and allergic phenotypes are consistent risk factors to develop indoor air quality (IAQ) respiratory complaints. The aim of this study was to compare the role of allergic rhinitis on respiratory complaints in individuals exposed to sudden temperature changes.

METHODS

To address this question, a case-control challenge study was performed in a laboratory of thermal comfort evaluation with twin isolated chambers set at 14 degrees C/57.2 degrees F (cold) and 26 degrees C/78.8 degrees F (hot) temperatures. A groups of 32 patients with persistent allergic rhinitis (rhinitis group) and 16 control subjects (control group) were exposed for 30 minutes, three times alternately in the chambers. Symptoms were reported using an analog visual scale and nasal and pulmonary peak flow measurements were taken during baseline at hot and cold temperatures and after the challenge.

RESULTS

The rhinitis group reported increased itching and stinging eyes when compared with the baseline during exposure to hot and cold temperatures and they also reported increased breathlessness during hot air exposure. In addition, there was a significant decrease in expiratory flow rates in this group during exposure to hot and cold temperatures that persisted for 24 hours after challenge.

CONCLUSION

This study suggests that individuals with allergic rhinitis have a lower threshold than controls to develop respiratory and ocular symptoms after air-conditioning-induced sudden temperature changes.

Prevalence of building-related symptoms as an indicator of health and productivity

BACKGROUND

The prevalence of building-related symptoms (BRS) is commonly used to characterize the indoor air quality in office buildings. To analyze the costs of building renovation and the improvement of the indoor environment, it is useful to quantitatively relate the prevalence or intensity of BRS to productivity. The intent of this study is to summarize the links between the BRS and productivity, and demonstrate this linkage in two case buildings.

MATERIAL AND METHODS

A literature was surveyed for studies that measured simultaneously the prevalence or intensity of BRS and subjectively reported or objectively measured productivity. Case studies in two office environments were performed. An association between the prevalence of BRS and productivity of workers in a call center and in an insurance office were investigated. In the first case study, the productivity was expressed using the direct productivity metrics, namely the number of telephone contacts during active working hours while in the second case, the productivity was assessed by using the data concerning sick leave rates.

RESULTS

Employees who report more BRS also have more often absences which relate to indoor environment quality (IEQ). Their productivity is lower than those who have better IEQ in their offices. Despite uncertainties related to the data concerning recorded sick leave and self-reported productivity, the number of studies showing an association between BRS and productivity or sick leave suggests that such a relationship exists. The present case studies also demonstrated an association between the BRS and the direct productivity. Based on the data from the call center, a reduction of 10%-units in the prevalence of general symptoms (such as fatigue, headache, nausea, etc.) corresponded with a gain of 1.5% in performance. Based on the findings in the insurance company, a reduction of 10%-units in the prevalence of irritation symptoms corresponded with a decrease of 0.7% in the short-term absenteeism.

CONCLUSIONS

A review of 23 studies suggests that a linkage exists between typical BRS and productivity indicators such as task or work performance or absence from work. Quantitative associations between BRS and productivity were demonstrated in two office environments. Quantitative associations between BRS and economic metrics enable cost-benefits analysis.

Persistent allergic rhinitis and indoor air quality perception--an experimental approach

In order to compare patterns of indoor air perception, including perceptions of temperature, air movement, indoor air quality (IAQ), mental concentration, and comfort, 33 subjects either with persistent allergic rhinitis or controls were exposed to different temperatures and constant relative humidity in an experimental office environment. Results were obtained by means of a self-administered visual analogue scale, analyzed using mean score comparisons and principal component analysis. At 14 degrees C, the rhinitis group reported higher scores for sensations of air dryness than controls. At 18 degrees C, in the rhinitis group, there was a correlation between dry, stagnant air, and difficult mental concentration. This group also correlated heat, dry air, and poor IAQ, in contrast to the control group, which correlated comfort, easy mental concentration, and freshness. At 22 degrees C, the rhinitis group correlated heat, dryness, stagnant air, and overall discomfort. This group also correlated non-dry air, freshness, and comfort, whereas the control group correlated heat, humidity, good indoor air, freshness, and comfort. This study suggests that the rhinitis group perceives indoor temperatures of 14 degrees C as dryer than controls do, and that at 18 and 22 degrees C this group positively correlates different adverse perceptions of IAQ. By means of a self-administered questionnaire in an experimental condition, the present study compares subjective patterns of indoor air perception from individuals with respiratory allergy (allergic rhinitis) to control individuals. It reports different patterns of perception of indoor air quality (IAQ) between the two groups, suggesting that allergic individuals could have different IAQ perception.

Ultraviolet germicidal irradiation disinfection of Stachybotrys chartarum

The ultraviolet germicidal irradiation (UVGI) dose necessary to inactivate fungal spores on an agar surface and the efficacy of UVGI were determined for cultures of Stachybotrys chartarum (ATCC 208877). This study employed a UVGI testing unit consisting of four chambers with a 9-W, Phillips, low pressure, mercury UVGI lamp in each chamber. The testing unit's apertures were adjusted to provide 50, 100, 150, and 200 µW/cm2 of uniform flux to the Petri dish surfaces, resulting in a total UVGI surface dose ranging from 12 to 144 mJ/cm2. The UVGI dose necessary to inactivate 90% of the S. chartarum was greater than the maximum dose of 144 mJ/cm2 evaluated in this study. While UVGI has been used to inactivate several strains of culturable fungal spores, S. chartarum was not susceptible to an appropriate dose of UVGI. The results of this study may not correlate directly to the effect of UVGI on airborne fungal spores. However, they indicate that current technology may not be efficacious as a supplement to ventilation unless it can provide higher doses of UVGI to kill spores, such as S. chartarum, traveling through the irradiated zone.Key words: Stachybotrys chartarum (synonyms S. atra, S. alternana), ultraviolet germicidal irradiation, fungi.

Microbial Contamination in Airplane Cabins:Health Effects and Remediation

Microorganisms that affect human health are found in all indoor environments, including cabins of commercial aircraft. Those that arise from human sources can be transmitted by direct contact, droplets, or the airborne route. Infections from human sources include Influenza, Rhinovirus, SARS and tuberculosis. Transmission by the airborne route can be reduced by sterilizing the air with ultraviolet germicidal irradiation, or by diluting the contaminated air with outdoor air through ventilation. Microbes arising from environmental sources include bacteria, fungi and other organisms such as protozoa. These usually have very simple requirements for growth – water and a simple substrate such as dust. They cause health effects through direct infection rarely (one example is Legionnella), but more commonly cause immune reactions resulting in hypersensitivity or allergy mediated diseases. Environmental sources of microbial contamination are best prevented, but can be remediated through cleaning, germicidal chemicals, or ultraviolet germicidal irradiation. Airborne microbial substances including toxins, antigens and viable organisms can be removed by outdoor air ventilation or filtration. In aircraft cabins transmission of pathogens from human sources is difficult to control, but airborne transmission can be reduced through increased outdoor air ventilation or filtration. Environmental microbial contamination can, and does occur in aircraft cabins. These microbial sources are best prevented but, if detected, can be removed through cleaning or disinfection. Ultraviolet germicidal irradiation is an under-utilized technology that may be useful for sterilizing air as well as potential environmental sources.

Health effects of indoor fungi

OBJECTIVE

To review the nontoxic harmful effects that poor indoor air quality caused by fungi can have on health.

DATA SOURCES

We searched PubMed for publications related to the various topics discussed in this review, and we relied on our knowledge of the field.

STUDY SELECTION

Where more than one publication was relevant, we attempted to identify a consensus of the reports and cited the most relevant articles. Priority was given to randomized controlled trials and expert reports when available, although much of the information herein relates to laboratory research.

RESULTS

Actively growing fungal colonies can release volatile substances that have an unpleasant smell, leading to psychological responses in the occupants such as fatigue and nausea. Symptoms that are likely caused by indoor fungi include respiratory complaints that involve the nose and lungs, eye symptoms, and mucous membrane irritation. These adverse effects can occur by a variety of mechanisms, including IgE-mediated hypersensitivity, fungal infection, irritant reaction to spores or fungal metabolites, and possibly toxic reaction to mycotoxins.

CONCLUSIONS

Reduced fungal exposure can reasonably be expected to improve health. Removal of moisture from the indoors and proper maintenance of air filters can aid in prevention and elimination of fungi from the home environment. Small areas of present contamination can be cleaned with a dilute bleach solution, which kills viable colonies and removes their mycelia. If fungal contamination is not addressed early, substantial damage can occur, requiring professional remediation. Above all, the individual should not panic at the first sight of fungi growing in the home. Regular inspection and cleaning can prevent many fungus-related problems.

Disinfection of selected Aspergillus spp. using ultraviolet germicidal irradiation

Aims: The efficacy of ultraviolet germicidal irradiation (UVGI) and the UVGI dose necessary to inactivate fungal spores on an agar surface for cultures of Aspergillus flavus and Aspergillus fumigatus were determined. Methods and results: A four-chambered UVGI testing unit with a 9-W, Phillips, low pressure, mercury UVGI lamp in each chamber was used in this study. An aperture was adjusted to provide 50, 100, 150, and 200 µW/cm2 of uniform flux to the surfaces of the Petri dish, resulting in a total UVGI dose to the surface of the Petri dishes ranging from 12 to 96 mJ/cm2. The UVGI dose necessary to inactivate 90% of the A. flavus and A. fumigatus was 35 and 54 mJ/cm2, respectively. Conclusions: UVGI can be used to inactivate culturable fungal spores. Aspergillus flavus was more susceptible than A. fumigatus to UVGI. Significance and impact of the study: These results may not be directly correlated to the effect of UVGI on airborne fungal spores, but they indicate that current technology may not be efficacious as a supplement to ventilation unless it can provide higher doses of UVGI to kill spores traveling through the irradiated zone.Key words: Aspergillus, ultraviolet germicidal irradiation, fungi.

Decreased Respiratory Symptoms After Intervention in Artificially Ventilated Offices in São Paulo, Brazil

BACKGROUND

The increase in work-related respiratory complaints in artificially ventilated buildings have multiple causes, and intervention studies are a valuable approach to understanding possible mechanisms.

STUDY OBJECTIVES

To analyze the effects of an intervention in a ventilation system with > 20 years of continuous use, and with a high rate of building-related respiratory complains.

DESIGN

An epidemiologic study was done among individuals working in places with ventilation machinery and ducts with > 20 years of use, before and after intervention. Analysis of symptoms and logistic regression were performed to check the associations between air-conditioning intervention and reported symptoms.

RESULTS

The air-conditioning intervention showed a protective effect on building-related worsening of respiratory symptoms (odds ratio, 0.132; 95% confidence interval, 0.030 to 0.575), naso-ocular symptoms (odds ratio, 0.231; 95% confidence interval, 0.058 to 0.915), and persistent cough (odds ratio, 0.071; 95% confidence interval, 0.014 to 0.356).

CONCLUSION

Intervention in high-risk occupational locations can be effective in improving perceived indoor air quality.

Effect of ultraviolet germicidal lights installed in office ventilation systems on workers' health and wellbeing: double-blind multiple crossover trial

BACKGROUND

Workers in modern office buildings frequently have unexplained work-related symptoms or combinations of symptoms. We assessed whether ultraviolet germicidal irradiation (UVGI) of drip pans and cooling coils within ventilation systems of office buildings would reduce microbial contamination, and thus occupants' work-related symptoms.

METHODS

We undertook a double blind, multiple crossover trial of 771 participants. In office buildings in Montreal, Canada, UVGI was alternately off for 12 weeks, then turned on for 4 weeks. We did this three times with UVGI on and three times with it off, for 48 consecutive weeks. Primary outcomes of self-reported work-related symptoms, and secondary outcomes of endotoxin and viable microbial concentrations in air and on surfaces, and other environmental covariates were measured six times.

FINDINGS

Operation of UVGI resulted in 99% (95% CI 67-100) reduction of microbial and endotoxin concentrations on irradiated surfaces within the ventilation systems. 771 participants appeared to remain masked, and reported no adverse effects. On the basis of within-person estimates, use of UVGI was associated with significantly fewer work-related symptoms overall (adjusted odds ratio 0.8 [95% CI 0.7-0.99]), as well as respiratory (0.6 [0.4-0.9]) and mucosal (0.7 [0.6-0.9]) symptoms than was non-use. Reduction of work-related mucosal symptoms was greatest among atopic workers (0.6 [0.5-0.8]), and never-smokers (0.7 [0.5-0.9]). With UVGI on, never-smokers also had large reduction of work-related respiratory (0.4 [0.2-0.9]), and musculoskeletal symptoms (0.5 [0.3-0.9]).

INTERPRETATION

Installation of UGVI in most North American offices could resolve work-related symptoms in about 4 million employees, caused by microbial contamination of heating, ventilation, and air-conditioning systems. The cost of UVGI installation could in the long run prove cost-effective compared with the yearly losses from absence because of building-related illness.

Upper respiratory symptoms associated with aging of the ventilation system in artificially ventilated offices in São Paulo, Brazil

BACKGROUND

The increase of work-related respiratory complaints in artificially ventilated buildings has multiple causes, and the role of allergen exposure and symptoms is still controversial.

STUDY OBJECTIVES

To analyze the risk factors and the association of work-related symptoms with allergen exposure and different conditions of the same air conditioning system in São Paulo, Brazil.

DESIGN

Workers were classified according to characteristics of the air conditioning system: the first group (group 1) with ventilation machinery and ducts with > 20 years of use, the second group (group 2) with ventilation machinery with > 20 years of use and ventilation ducts with < 2 years of use, and the third group (group 3) with ventilation machinery and ducts with < 2 years of use. Logistic regression was performed to check the associations between air conditioning groups, allergen exposure (fungi, mites, animal dander, and cockroach), and symptoms.

RESULTS

There was a higher prevalence of building-related worsening of respiratory symptoms (p = 0.004; odds ratio [OR], 8.53) and symptoms of rhinoconjunctivitis (p = 0.01; OR, 8.49) in group 1. There was a lower relative humidity (p = 0.05) and nonsignificant lower temperature in group 1, when compared to the other groups. The viable mold spores totals were higher outdoors than in the indoor samples (n = 45, p = 0.017). There were higher levels of Der p 1 in group 2 (p = 0.032). All allergen levels were considered low.

CONCLUSION

There was a strong association of building-related upper-airway symptoms with places having ventilation systems with > 20 years of use.

Medical aspects of global warming

BACKGROUND

Global warming is caused by increased carbon dioxide (CO2)resulting in a greenhouse effect with enhanced warming of the earth. Measurements of CO2 show a steady increase over the past 30 years caused by the burning of fossil fuels and from the loss of natural CO2 sinks. A 100-year increase in global temperature by 0.3 to 0.6 degrees C is reflected in atmospheric warming, glacier shrinkage, and rising sea levels.

OBJECTIVES

Planetary ecosystem dynamics are being altered, challenging public health. It is predicted that morbidity and mortality will increase as a result of heat stress, as seen in recent heat waves in the U.S. Weather disaster effects will increase in number and magnitude, and both noninfectious and infectious diseases may flourish. A significant challenge will be the changes in life cycles of microbial species due to the warmer environs. Specific increases in incidence have been noted for vector-borne diseases, in addition to pulmonary findings, cardiovascular morbidity, neurological diseases, and occupational diseases.

CONCLUSIONS

Warming can be demonstrated by the observed changes that have already occurred in the environment, particularly the thinning of polar ice caps. The United States Global Research Program has been established to coordinate research activities, which responds to issues deemed important by the United Nations Framework Convention on Climate Change. Research issues pertain to the scientific uncertainties in the greenhouse effect, temperature measurements at various atmospheric levels and latitudes, and impact on biota redistribution. The Kyoto Protocol has mandated specific solutions, e.g., a 7% reduction in CO2 levels within 10 years. Future recommendations involve supporting new technologies that are available to decrease emissions as well as understanding the role that occupational and environmental specialists have in global warming recognition.

Effectiveness of germicidal UV radiation for reducing fungal contamination within air-handling units

Levels of fungi growing on insulation within air-handling units (AHUs) in an office building and levels of airborne fungi within AHUs were measured before the use of germicidal UV light and again after 4 months of operation. The fungal levels following UV operation were significantly lower than the levels in control AHUs.