Indoor Particle Levels Research Articles

Particle characterization in commercial buildings: A cross-sectional study in 40 offices in Singapore

There is a knowledge gap in understanding how existing office buildings are protecting occupants from exposure to particles from both indoor and outdoor sources. We report a cross-sectional study involving weekly measurements of size-resolved indoor and outdoor particle concentrations in forty commercial building offices in Singapore. The outdoor and indoor particles size distributions were single mode with daytime peak number concentrations at 36.5 nm and 48.7 nm. Outdoor concentrations were significantly greater than indoors for all particle diameters. Indoor particle concentrations were generally low due to: 1) relatively high indoor particle removal (IPR) rates; 2) low indoor source strengths; and 3) low indoor particle of outdoor proportion (IPOP). We found that the ventilation system type had a substantial effect on indoor particle levels, IPR and IPOP. Through linear mixed model analyses, we identified dependencies of IPR rates with the use of MERV13 filters in supply air and filter maintenance frequency, IPOP with the use of MERV13 filters in the fresh air and supply air ducts and low particle source strength with regular daily cleaning presumably due to dust reservoir removal. Lastly, the contribution of outdoor sources was mainly seen for ultrafine and fine particles but less pronounced for coarse particles. This study provided detailed understanding of particle exposure in building offices and their influencing factors, facilitating future research on health impact of particle exposures.

Revealing Long-Term Indoor Air Quality Prediction: An Intelligent Informer-Based Approach.

Indoor air pollution is an urgent issue, posing a significant threat to the health of indoor workers and residents. Individuals engaged in indoor occupations typically spend an average of around 21 h per day in enclosed spaces, while residents spend approximately 13 h indoors on average. Accurately predicting indoor air quality is crucial for the well-being of indoor workers and frequent home dwellers. Despite the development of numerous methods for indoor air quality prediction, the task remains challenging, especially under constraints of limited air quality data collection points. To address this issue, we propose a neural network capable of capturing time dependencies and correlations among data indicators, which integrates the informer model with a data-correlation feature extractor based on MLP. In the experiments of this study, we employ the Informer model to predict indoor air quality in an industrial park in Changsha, Hunan Province, China. The model utilizes indoor and outdoor temperature, humidity, and outdoor particulate matter (PM) values to forecast future indoor particle levels. Experimental results demonstrate the superiority of the Informer model over other methods for both long-term and short-term indoor air quality predictions. The model we propose holds significant implications for safeguarding personal health and well-being, as well as advancing indoor air quality management practices.

Assessing the effectiveness of portable HEPA air cleaners for reducing particulate matter exposure in King County, Washington homeless shelters: Implications for community congregate settings

Over four thousand portable air cleaners (PACs) with high-efficiency particulate air (HEPA) filters were distributed by Public Health - Seattle & King County to homeless shelters during the COVID-19 pandemic. This study aimed to evaluate the real-world effectiveness of these HEPA PACs in reducing indoor particles and understand the factors that affect their use in homeless shelters. Four rooms across three homeless shelters with varying geographic locations and operating conditions were enrolled in this study. At each shelter, multiple PACs were deployed based on the room volume and PAC's clean air delivery rate rating. The energy consumption of these PACs was measured using energy data loggers at 1-min intervals to allow tracking of their use and fan speed for three two-week sampling rounds, separated by single-week gaps, between February and April 2022. Total optical particle number concentration (OPNC) was measured at 2-min intervals at multiple indoor locations and an outdoor ambient location. The empirical indoor and outdoor total OPNC were compared for each site. Additionally, linear mixed-effects regression models (LMERs) were used to assess the relationship between PAC use time and indoor/outdoor total OPNC ratios (I/OOPNC). Based on the LMER models, a 10 % increase in the hourly, daily, and total time PACs were used significantly reduced I/OOPNC by 0.034 [95 % CI: 0.028, 0.040; p < 0.001], 0.051 [95 % CI: 0.020, 0.078; p < 0.001], and 0.252 [95 % CI: 0.150, 0.328; p < 0.001], respectively, indicating that keeping PACs on resulted in significantly lower I/OOPNC. The survey suggested that keeping PACs on and running was the main challenge when operating them in shelters. These findings suggested that HEPA PACs were an effective short-term strategy to reduce indoor particle levels in community congregate living settings during non-wildfire seasons and the need for formulating practical guidance for using them in such an environment.

Experimental and numerical analysis of indoor air quality affected by outdoor air particulate levels (PM1.0, PM2.5 and PM10), room infiltration rate, and occupants' behaviour

This study conducted an experimental analysis of how indoor air quality (IAQ) is influenced by the outdoor air pollutants levels, infiltration rate, and occupants' behaviours. The impacts of these factors on IAQ were analyzed using on-site measurements and numerical simulations. The results contribute to a better understanding of how to control the Indoor Particulate Level (IPL) for the specific conditions of the studied building. Results showed that occupant behaviour was the primary factor in determining the IPL, significantly changing the number of outdoor particles introduced to the building. Moreover, it was found that the IPL was exponentially correlated to the Outdoor Particulate Level (OPL). Based on numerical simulations, this study concluded that smaller particles do not always have more chance than larger particles of accessing the indoor environment through the building envelope. Meanwhile, a steady-state indoor particle concentration numerical model was established and verified using the 4-fold cross-validation method. Finally, simulation results identified that the room infiltration rate had a positive linear impact on IAQ if the OPL was under 30 μg/m3. This is because the increased air exchange rate can help to dilute indoor air pollutants when the outdoor air is relatively clean.

Personal Exposure and Inhaled Dose Estimation of Air Pollutants during Travel between Albany, NY and Boston, MA

Out of eight deaths caused worldwide, one death is caused due to air pollution exposure, making it one of the top global killers. Personal exposure measurement for real-time monitoring has been used for inhaled dose estimation during various modes of workplace commuting. However, dose-exposure studies during long commutes are scarce and more information on inhaled doses is needed. This study focuses on personal exposures to size-fractionated particulate matter (PM1, PM2.5, PM4, PM7, PM10, TSP) and black carbon (BC) inside a bus traveling more than 270 kms on a highway between Albany, NY and Boston, MA. Measurements were also made indoors, outdoors, and while walking in each city. Mean PM (PM1, PM2.5, PM4, PM7, PM10, TSP) and mean BC concentrations were calculated to estimate the inhaled exposure dose. The highest average PM2.5 and PM10 exposures concentrations were 30 ± 12 and 111 ± 193 µg/m3, respectively, during Boston to Albany. Notably, personal exposure to BC on a bus from Albany to Boston (5483 ± 2099 ng/m3) was the highest measured during any commute. The average inhaled dose for PM2.5 during commutes ranged from 0.018 µg/km to 0.371 µg/km. Exposure concentrations in indoor settings (average PM2.5 = 37 ± 55 µg/m3, PM10 = 78 ± 82 µg/m3, BC = 5695 ± 1774 ng/m3) were higher than those in outdoor environments. Carpeted flooring, cooking, and vacuuming all tended to increase the indoor particulate level. A high BC concentration (1583 ± 1004 ng/m3) was measured during walking. Typical concentration profiles in long-haul journeys are presented.

Ventilation strategies on indoor particles in day-care center

In this study, a day-care center located in Seoul was monitored for one year to quantify the effects of ventilation methods, natural and mechanical, on the indoor particle levels. It is found from the field monitoring that air tightness and mechanical ventilation system with MERV 12 can be helpful to maintain indoor particles at low levels during the class hours of the day-care center. The mechanical ventilation, however, is not sufficient for lowering PM2.5 when the outdoor PM2.5 is at high levels.

Impact of ironing on indoor particle levels and composition

Domestic chores are an important part of the household's daily routine and can contribute significantly to personal exposure. In this study, the particulate mass and number concentrations were assessed when using two irons (steam iron and steam iron with boiler) under distinct conditions (minimum ventilation and indoor doors open) and in the background air. The detailed PM10 chemical characterisation included organic and elemental carbon, elements and organic speciation. Particle number emission rates ranged from 8.1 ± 0.09 × 1011 to 15 ± 3.5 × 1011 particles min−1. Ratios of peak to background levels indicate that ironing can elevate the ultrafine particle number concentrations by a factor ranging from 35 to 194. PM10 emission rates from steam iron, under minimum ventilation conditions (6.6 ± 1.4 μg s−1), were higher than those from steam iron with the doors open (1.9 ± 1.6 μg s−1). The highest particle number and mass emission rates were recorded when the steam iron with boiler was used. Regarding the chemical composition of particles, elemental carbon and strontium were only detected during ironing. Bromide concentrations increased noticeably over background levels (9–51 times) during ironing. PM10 samples encompassed a wide range of organic compounds, part of which can be attributed to the handling of textiles and the use of detergents, fabric softeners, cosmetics and personal care products. Substances emitted by volatilisation or shedding of textile fibres, or due to handling, can contribute to human exposure through inhalation. The cancer risks associated with inhalation of metals and PAH were found to be negligible.

Investigating the impact of filters on long-term particle concentration measurements in residences (RP-1649)

Filters in heating, ventilation, and air-conditioning (HVAC) systems are the most prevalent air cleaning method in residential environments in North America. This study evaluated the long-term impact of residential filtration systems on indoor particle concentrations by examining concentration measurements from low-cost monitors over one year in twenty homes in Toronto, Ontario, Canada. These concentration results suggested that in general, indoor concentration had a similar seasonal trend as the ambient concentration, and indoor activities (e.g., cooking) elevated indoor particle levels for 40-50% of the time. Further, the impacts of electret filters were examined using a non-electret filter with a minimum efficiency reporting value (MERV) of 8 as the reference point at each home. The mean effectiveness of the filters (MERV 8E = −4.19%, MERV 11E = −0.51%, and MERV 14E = 14.5%) were lower than values found in the literature, most likely due to lower HVAC system runtime in our sample of homes (median = 9.6%). Overall, this filter effectiveness analysis reveals that the real-life filter performance was strongly influenced by system and house characteristics (e.g., system runtime, in-situ efficiency, air change rate, and particle source strength), and thus can be different from modeling and laboratory test results.

Randomised controlled trial of real-time feedback and brief coaching to reduce indoor smoking

BackgroundPrevious secondhand smoke (SHS) reduction interventions have provided only delayed feedback on reported smoking behaviour, such as coaching, or presenting results from child cotinine assays or air particle counters.DesignThis SHS...

Energy consumption, indoor thermal comfort and air quality in a commercial office with retrofitted heat, ventilation and air conditioning (HVAC) system

Retrofit on existing buildings for better energy performance is widely desired due to large share of building energy consumption. Meanwhile, the importance of thermal comfort and air pollution exposure has attracted increasing attention for occupant health, productivity and sustainable development. Heat, ventilation and air conditioning (HVAC) systems are responsible for a substantial proportion of energy use in buildings and are closely related to indoor environment quality. This study examined the energy consumption and indoor environment in a commercial office building with a retrofitted HVAC system. The retrofitting measures included a sensor-based building management system, dehumidification of outdoor air, and a two-stage particle filtration system. Energy data were collected before and after the retrofit. Field measurements were conducted in both winter and summer to evaluate the thermal comfort and indoor exposure to air pollutants in the retrofitted area. An experiment was designed to assess the benefits of upgraded filters on exposure to ambient particles during summer. By combining all of these measures, the retrofitted HVAC system was able to reduce energy use by 50% while maintaining generally acceptable indoor thermal comfort. Most of the time, the indoor particle levels complied with the World Health Organization's guidelines. The upgraded filtration system with a pleated filter reduced outdoor PM ingress by 30% to 60% more than the aluminum filter used before the retrofit. Co-benefit assessment provides insights into sustainability in building development during a retrofit by holistically examining energy use and the environment.

Ultrafine and Fine Particulate Matter Inside and Outside of Mechanically Ventilated Buildings.

The objectives of this study were to measure levels of particulate matter (PM) in mechanically ventilated buildings and to improve understanding of filtration requirements to reduce exposure. With the use of an Ultra High Sensitivity Aerosol Spectrometer and an Aerodyne Mass Spectrometer, ultrafine (0.055–0.1 μm) and fine (0.1–0.7 μm) indoor and outdoor PM was measured as a function of time in an office, a university building, and two elementary schools. Indoor particle levels were highly correlated with outdoor levels. Indoor and outdoor number concentrations in Denver were higher than those in Boulder, with the highest number concentrations occurring during summer and fall. The ratio of indoor-to-outdoor (I/O) PM was weakly but positively correlated with the amount of ventilation provided to the indoor environment, did not vary much with particle size (ranged between 0.48 and 0.63 for the entire size range), and was similar for each period of the week (weekend vs. weekday, night vs. day). Regression analyses showed that ultrafine indoor PM baseline concentrations were higher at night from nighttime infiltration. A lag time was observed between outdoor and indoor measurements. Weekday days had the shortest lag time of 11 min, and weekend nighttime lags when the HVAC was not in use were 50 to 148 min. Indoor-outdoor PM concentration plots showed ultrafine PM was more correlated compared to fine, and especially when the HVAC system was on. Finally, AMS data showed that most of the PM was organic, with occasional nitrate events occurring outdoors. During nitrate events, there were less indoor particles detected, indicating a loss of particulate phase nitrate. The results from this study show that improved filtration is warranted in mechanically ventilated buildings, particularly for ultrafine particles, and that nighttime infiltration is significant depending on the building design.

Numerical assessment of the effect of cigarette smoking on indoor PM2.5 distribution and study of ventilation strategies

Elevated concentration of indoor particulate matter (PM) has been linked to adverse effects on human health. To explore how particles from cigarette smoke affect the indoor PM2.5 concentration and whether such circumstance is harmful to people, distribution characteristics of indoor particulate matter in a typical residence with a smoker were numerically studied under different ventilation strategies. The indoor PM2.5 concentration without forced ventilation was shown to far exceed the air quality standard of 75 µg/m3 as recommended by the World Health Organization. In this study, we numerically investigated the performances of the mixing and displacement ventilation strategies in reducing indoor particle levels. Different airflow patterns could significantly influence the movement and deposition of particles in ventilated rooms, even with the same air change rate and particle characteristics. When comparing with the mixing ventilation strategy, the displacement ventilation strategy was shown to have a lower deposition mass and a larger portion of particles leaving the room. Thus, the average indoor PM2.5 concentration in the displacement ventilation strategy was shown to be higher than the mixing ventilation strategy. In spite of this, low particle concentration in the personnel’s breathing zone was shown by our measurement. Displacement ventilation strategy could provide a cleaner ambient air than the mixing one.

Ozone, Electrostatic Precipitators, and Particle Number Concentrations: Correlations Observed in a Real Office during Working Hours

This study investigates the impacts of outdoor and indoor ozone concentrations, ESP operation and occupancy on particle number concentrations within a modern office in Changsha, China. The office's one-pass air handling system contains a mini-bag filter (MERV 12) followed by an electrostatic precipitator (ESP) and high efficiency particulate air (HEPA) filter. Over a five-week period the system was operated either without the ESP (Stage 1, first-third week) or with the ESP (Stage 2, fourth and fifth week). Ozone and particle number concentrations were measured on working days. During both stages, indoor ozone and particle number concentrations tracked the outdoor ozone concentration. When operating, the ESP produced approximately 29 mg h(-1) of ozone, increasing supply air ozone by 15 ppb and steady-state indoor ozone by about 3 ppb. Occupancy tended to decrease indoor ozone and increase particle levels. During occupancy, indoor particle levels were low (∼2600 particle/cm(3)) when the supply air ozone level was less than 18 ppb. Above this threshold, the supply air ozone concentration and indoor particle number concentration were linearly related, and ESP operation increased the average indoor particle level by about 22 000 particles/cm(3). The implications for worker exposure to both ozone and particles are discussed.

Continuous weeklong measurements of indoor particle levels in a Minnesota Tribal Casino Resort

BackgroundSecondhand smoke (SHS) exposure for workers and patrons in hospitality venues is a persistent and significant public health concern. We designed this study to provide a comprehensive assessment of SHS exposure inside an Indian Tribal Casino in Minnesota.MethodsReal-time fine particulate matter (PM2.5) concentrations were measured at multiple locations for up to 7 days. The field monitoring provided information on the day of week and time of day variation of SHS exposure, as well as comparisons between smoking and non-smoking areas.ResultsIndoor PM2.5 level was nearly 13 times the concurrent outdoor PM2.5 level. Gaming floor hourly PM2.5 level was highest on Saturday night, averaged at 62.9 μg/m3. Highest PM2.5 concentration was observed in smoking-permitted employee break room, reaching 600 μg/m3. PM2.5 readings in non-smoking sections exhibited same temporal pattern as the readings in smoking sections.ConclusionsThe results show that indoor concentration of PM2.5 is substantially higher than the outdoor level, posing health risks to casino workers and patrons. SHS can migrate into adjacent non-smoking areas very quickly. The casino’s ventilation system did not fully eliminate SHS. A completely smoke-free casino would be the only way to fully protect non-smoking patrons and employees from the dangers of tobacco smoke.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-016-3553-4) contains supplementary material, which is available to authorized users.

Characterization of particulate matter concentrations and bioaerosol on each floor at a building in Seoul, Korea.

Particulate matter (PM) in buildings are mostly sourced from the transport of outdoor particles through a heating, ventilation, and air conditioning (HVAC) system and generation of particle within the building itself. We investigated the concentrations and characteristic of indoor and outdoor particles and airborne bacteria concentrations across four floors of a building located in a high-traffic area. In all the floors we studied (first, second, fifth, and eighth), the average concentrations of particles less than 10 μm (PM10) in winter for were higher than those in summer. On average, a seasonal variation in the PM10 level was found for the first, fifth, and eighth floors, such that higher values occurred in the winter season, compared to the summer season. In addition, in winter, the indoor concentrations of PM10 on the first, fifth, and eighth floors were higher than those of the outdoor PM10. The maximum level of airborne bacteria concentration was found in a fifth floor office, which held a private academy school consisting of many students. Results indicated that the airborne bacteria remained at their highest concentration throughout the weekday period and varied by students' activity. The correlation coefficient (R (2)) and slope of linear approximation for the concentrations of particulate matter were used to evaluate the relationship between the indoor and outdoor particulate matter. These results can be used to predict both the indoor particle levels and the risk of personal exposure to airborne bacteria.

Effects of types of ventilation system on indoor particle concentrations in residential buildings.

The objective of this study was to quantify the influence of ventilation systems on indoor particle concentrations in residential buildings. Fifteen occupied, single-family apartments were selected from three sites. The three sites have three different ventilation systems: unbalanced mechanical ventilation, balanced mechanical ventilation, and natural ventilation. Field measurements were conducted between April and June 2012, when outdoor air temperatures were comfortable. Number concentrations of particles, PM2.5 and CO2 , were continuously measured both outdoors and indoors. In the apartments with natural ventilation, I/O ratios of particle number concentrations ranged from 0.56 to 0.72 for submicron particles, and from 0.25 to 0.60 for particles larger than 1.0 μm. The daily average indoor particle concentration decreased to 50% below the outdoor level for submicron particles and 25% below the outdoor level for fine particles, when the apartments were mechanically ventilated. The two mechanical ventilation systems reduced the I/O ratios by 26% for submicron particles and 65% for fine particles compared with the natural ventilation. These results showed that mechanical ventilation can reduce exposure to outdoor particles in residential buildings. Results of this study confirm that mechanical ventilation with filtration can significantly reduce indoor particle levels compared with natural ventilation. The I/O ratios of particles substantially varied at the naturally ventilated apartments because of the influence of variable window opening conditions and unsteadiness of wind flow on the penetration of outdoor air particles. For better prediction of the exposure to outdoor particles in naturally ventilated residential buildings, it is important to understand the penetration of outdoor particles with variable window opening conditions.

Airborne particulate matter in school classrooms of northern Italy.

Indoor size-fractioned particulate matter (PM) was measured in seven schools in Milan, to characterize their concentration levels in classrooms, compare the measured concentrations with the recommended guideline values, and provide a preliminary assessment of the efficacy of the intervention measures, based on the guidelines developed by the Italian Ministry of Healthand applied to mitigate exposure to undesirable air pollutants. Indoor sampling was performed from Monday morning to Friday afternoon in three classrooms of each school and was repeated in winter 2011–2012 and 2012–2013. Simultaneously, PM2.5 samples were also collected outdoors. Two different photometers were used to collect the PM continuous data, which were corrected a posteriori using simultaneous gravimetric PM2.5 measurements. Furthermore, the concentrations of carbon dioxide (CO2) were monitored and used to determine the Air Exchange Rates in the classrooms. The results revealed poor IAQ in the school environment. In several cases, the PM2.5 and PM10 24 h concentrations exceeded the 24 h guideline values established by the World Health Organization (WHO). In addition, the indoor CO2 levels often surpassed the CO2 ASHRAE Standard. Our findings confirmed that important indoor sources (human movements, personal clouds, cleaning activities) emitted coarse particles, markedly increasing the measured PM during school hours. In general, the mean PM2.5 indoor concentrations were lower than the average outdoor PM2.5 levels, with I/O ratios generally <1. Fine PM was less affected by indoor sources, exerting a major impact on the PM1–2.5 fraction. Over half of the indoor fine particles were estimated to originate from outdoors. To a first approximation, the intervention proposed to reduce indoor particle levels did not seem to significantly influence the indoor fine PM concentrations. Conversely, the frequent opening of doors and windows appeared to significantly contribute to the reduction of the average indoor CO2 levels.

Indoor Particle Levels in Small- and Medium-Sized Commercial Buildings in California

This study monitored indoor and outdoor particle concentrations in 37 small and medium commercial buildings (SMCBs) in California with three buildings sampled on two occasions, resulting in 40 sampling days. Sampled buildings included offices, retail establishments, restaurants, dental offices, and hair salons, among others. Continuous measurements were made for both ultrafine and fine particulate matter as well as black carbon inside and outside of the building. Integrated PM(2.5), PM(2.5-10), and PM(10) samples were also collected inside and outside the building. The majority of the buildings had indoor/outdoor (I/O) particle concentration ratios less than 1.0, indicating that contributions from indoor sources are less than removal of outdoor particles. However, some of the buildings had I/O ratios greater than 1, indicating significant indoor particle sources. This was particularly true of restaurants, hair salons, and dental offices. The infiltration factor was estimated from a regression analysis of indoor and outdoor concentrations for each particle size fraction, finding lower values for ultrafine and coarse particles than for submicrometer particles, as expected. The I/O ratio of black carbon was used as a relative measure of the infiltration factor of particles among buildings, with a geometric mean of 0.62. The contribution of indoor sources to indoor particle levels was estimated for each building.

Chemical Characterization and Source Apportionment of Fine and Coarse Particulate Matter Inside the Refectory of Santa Maria Delle Grazie Church, Home of Leonardo Da Vinci’s “Last Supper”

The association between exposure to indoor particulate matter (PM) and damage to cultural assets has been of primary relevance to museum conservators. PM-induced damage to the "Last Supper" painting, one of Leonardo da Vinci's most famous artworks, has been a major concern, given the location of this masterpiece inside a refectory in the city center of Milan, one of Europe's most polluted cities. To assess this risk, a one-year sampling campaign was conducted at indoor and outdoor sites of the painting's location, where time-integrated fine and coarse PM (PM(2.5) and PM(2.5-10)) samples were simultaneously collected. Findings showed that PM(2.5) and PM(2.5-10) concentrations were reduced indoors by 88 and 94% on a yearly average basis, respectively. This large reduction is mainly attributed to the efficacy of the deployed ventilation system in removing particles. Furthermore, PM(2.5) dominated indoor particle levels, with organic matter as the most abundant species. Next, the chemical mass balance model was applied to apportion primary and secondary sources to monthly indoor fine organic carbon (OC) and PM mass. Results revealed that gasoline vehicles, urban soil, and wood-smoke only contributed to an annual average of 11.2 ± 3.7% of OC mass. Tracers for these major sources had minimal infiltration factors. On the other hand, fatty acids and squalane had high indoor-to-outdoor concentration ratios with fatty acids showing a good correlation with indoor OC, implying a common indoor source.

Environmental and occupational allergies

Airborne allergens are the major cause of allergic rhinitis and asthma. Daily exposure comes from indoor sources, chiefly at home but occasionally at schools or offices. Seasonal exposure to outdoor allergens, pollens, and molds is another important source. Exposure to unusual substances at work causes occupational asthma, accounting for about 5% of asthma in adults. Indoor and outdoor air pollutants trigger airway inflammation and increase the severity of asthma. Diesel exhaust particles increase the production of IgE antibodies. Identification and reduction of exposure to allergens is a very important part of the management of respiratory allergic diseases. The first section of this chapter discusses domestic allergens, arthropods (mites and cockroaches), molds, and mammals (pets and mice). Indoor humidity and water damage are important factors in the production of mite and mold allergens, and discarded human food items are important sources of proliferation of cockroaches and mice. Means of identifying and reducing exposure are presented. The second section discusses outdoor allergens: pollens and molds. The particular plants or molds and the amount of exposure to these allergens is determined by the local climate, and local pollen and mold counts are available to determine the time and amount of exposure. Climate change is already having an important effect on the distribution and amount of outdoor allergens. The third section discusses indoor and outdoor air pollution and methods that individuals can take to reduce indoor pollution in addition to eliminating cigarette smoking. The fourth section discusses the diagnosis and management of occupational asthma.