Health effects and sources of indoor air pollution. Part I

Since the early 1970s, the health effects of indoor air pollution have been investigated with increasing intensity. Consequently, a large body of literature is now available on diverse aspects of indoor air pollution: sources, concentrations, health effects, engineering, and policy. This review begins with a review of the principal pollutants found in indoor environments and their sources. Subsequently, exposure to indoor air pollutants and health effects are considered, with an emphasis on those indoor air quality problems of greatest concern at present: passive exposure to tobacco smoke, nitrogen dioxide from gas-fueled cooking stoves, formaldehyde exposure, radon daughter exposure, and the diverse health problems encountered by workers in newer sealed office buildings. The review concludes by briefly addressing assessment of indoor air quality, control technology, research needs, and clinical implications.     

Excess dampness and mold growth in homes: an evidence-based review of the aeroirritant effect and its potential causes.

Exposure to fungi produces respiratory disease in humans through both allergic and nonallergic mechanisms. Occupants of homes with excess dampness and mold growth often present to allergists with complaints of aeroirritant symptoms. This review describes the major epidemiological and biological studies evaluating the association of indoor dampness and mold growth with upper respiratory tract symptoms. The preponderance of epidemiological data supports a link between exposure to dampness and excess mold growth and the development of aeroirritant symptoms. In addition, biological and clinical studies evaluating potential causal substances for the aeroirritant effect, notably volatile organic compounds (VOCs), are examined in detail. These studies support the role of VOCs in contributing to the aeroirritant symptoms of occupants of damp and mold-contaminated homes.     

Fungal Exposure and Asthma: IgE and Non-IgE-Mediated Mechanisms

Fungi are ubiquitous in indoor and outdoor environments and have been associated with respiratory disease including childhood and adult asthma. A growing body of evidence from human and animal studies has revealed a link between fungal exposure, especially indoor fungal exposure, with asthma initiation, persistence, and exacerbation. Despite the overwhelming evidence linking mold exposure and asthma, the mechanistic basis for the association has remained elusive. It is now clear that fungi need not be intact to impart negative health effects. Fungal components and fungal fragments are biologically active and contribute to asthma development and severity. Recent mechanistic studies have demonstrated that fungi are potent immunomodulators and have powerful effects on asthma independent of their potential to act as antigens. This paper will review the connection between fungal exposure and asthma with a focus on the immunological mechanisms underlying this relationship.     

Respiratory health effects of the indoor environment in a population of Dutch children

The effect of indoor exposure to nitrogen dioxide on respiratory health was studied over a period of 2 yr in a population of nonsmoking Dutch children 6 to 12 yr of age. Lung function was measured at the schools, and information on respiratory symptoms was collected from a self-administered questionnaire completed by the parents of the children. Nitrogen dioxide was measured in the homes of all children with Palmes' diffusion tubes. In addition, information on smoking and dampness in the home was collected by questionnaire. There was no relationship between exposure to nitrogen dioxide in the home and respiratory symptoms. Respiratory symptoms were found to be associated with exposure to tobacco smoke and home dampness. There was a weak, negative association between maximal midexpiratory flow (MMEF) and exposure to nitrogen dioxide. FEV1, peak expiratory flow, and MMEF were all negatively associated with exposure to tobacco smoke. Home dampness was not associated with pulmonary function. Lung function growth, measured over a period of 2 yr, was not consistently associated with any of the indoor exposure variables. The development of respiratory symptoms over time was not associated with indoor exposure to nitrogen dioxide. There was a significant association between exposure to environmental tobacco smoke in the home and the development of wheeze. There was also a significant association between home dampness and the development of cough.     

Clinical implications of mycotoxins and Stachybotrys

There has been considerable interest and concern in recent years regarding the potential health effects of mycotoxins in the indoor environment. Although the existence of mycotoxins has been known for several decades, relatively little is known about their effects in humans. What is known comes almost exclusively from studies of ingestion as the route of exposure. This review summarizes what is known regarding health effects of mycotoxins in general and specifically examines the evidence for the role of indoor exposure to the fungi of the genus Stachybotrys as a cause of disease in humans. Much work remains to be done in the area of mycotoxin research. The risk of health effects from ingestion seems much more widespread than from indoor airborne exposure, although the latter has received considerably more media attention. Rigorously controlled studies are needed to clarify these issues.     

Assessment of Environmental Cockroach Allergen Exposure

In the past, cockroach allergen exposure assessment mainly focused on settled dust in homes in low-income urban cities in the United States. That choice was not wrong; without measureable levels of cockroach allergen, it is difficult to show associations with any home characteristics, much less with health outcomes (e.g., allergy, asthma). However, recent studies in other suburban areas, schools, and other countries have elucidated the importance of cockroach allergen in these environments too. In addition, characterizing the underlying factors that give rise to cockroach allergen exposure (or protect against it) can lead to more targeted public health interventions. This review discusses different approaches to sampling indoor environments, interprets recent asthma and allergy studies, compares cockroach allergen levels from past studies with those of recent studies, and describes strategies for decreasing exposures.     

Indoor fungal composition is geographically patterned and more diverse in temperate zones than in the tropics

Fungi are ubiquitous components of indoor human environments, where most contact between humans and microbes occurs. The majority of these organisms apparently play a neutral role, but some are detrimental to human lifestyles and health. Recent studies that used culture-independent sampling methods demonstrated a high diversity of indoor fungi distinct from that of outdoor environments. Others have shown temporal fluctuations of fungal assemblages in human environments and modest correlations with human activity, but global-scale patterns have not been examined, despite the manifest significance of biogeography in other microbial systems. Here we present a global survey of fungi from indoor environments (n = 72), using both taxonomic and phylogeny-informative molecular markers to determine whether global or local indoor factors determine indoor fungal composition. Contrary to common ecological patterns, we show that fungal diversity is significantly higher in temperate zones than in the tropics, with distance from the equator being the best predictor of phylogenetic community similarity. Fungal composition is significantly auto-correlated at the national and hemispheric spatial scales. Remarkably, building function has no significant effect on indoor fungal composition, despite stark contrasts between architecture and materials of some buildings in close proximity. Distribution of individual taxa is significantly range- and latitude-limited compared with a null model of randomized distribution. Our results suggest that factors driving fungal composition are primarily global rather than mediated by building design or function.     

Influences of the community and consumer nutrition environment on the food purchases and dietary behaviors of adolescents: A systematic review

Adolescence is a period of increased autonomy over decision-making, including food choices, and increased exposure to influences outside the home, including the food environment. This review aims to synthesize the evidence for the influence of community nutrition environments, spatial access to food outlets, and consumer nutrition environments, environments inside food outlets, on adolescent food purchasing and dietary behaviors in high-income countries. Six databases were searched for articles published before January 2023. Results were synthesized using a vote-counting technique and effect direction plots that record the direction of the effect in relation to the anticipated relationship with health. Thirty-four observational and two intervention studies met the inclusion criteria. In the 13 studies assessing adolescent exposure to healthy community nutrition environments, results did not show clear associations with dietary and purchasing outcomes. Thirty studies assessed adolescents' exposure to unhealthy community nutrition environments with the majority (n = 17/30, 57%) reporting results showing that greater exposure to food outlets classified as unhealthy was associated with less healthy food purchases and dietary intakes. Inconsistent results were observed across the seven studies investigating associations with the consumer environment. Further research in these areas, including more high-quality intervention studies, may help to develop policy strategies to improve adolescents' dietary behaviors.     

Impact of stressor exposure on the interplay between commensal microbiota and host inflammation

Exposure to stressful stimuli results in the activation of multiple physiological processes aimed at maintaining homeostasis within the body. These physiological processes also have the capacity to influence the composition of microbial communities, and research now indicates that exposure to stressful stimuli leads to gut microbiota dysbiosis. While the relative abundance of many different bacterial types can be altered during stressor exposure, findings in nonhuman primates and laboratory rodents, as well as humans, indicate that bacteria in the genus Lactobacillus are consistently reduced in the gut during stress. The gut microbiota, including the lactobacilli, have many functions that enhance the health of the host. This review presents studies involving germfree and antibiotic treated mice, as well as mice given Lactobacillus spp. to prevent stressor-induced reductions in lactobacilli, to provide evidence that the microbiota contribute to stressor-induced immunomodulation, both in gut mucosa as well as in systemic compartments. This review will also discuss the evidence that commensal gut microbes have bidirectional effects on gastrointestinal physiology during stressor exposure.     

屋尘提取物暴露对过敏性哮喘的免疫调节机制

人们大部分时间是在室内度过的,特别是婴幼儿.室内环境对生命早期免疫的成熟影响极大.屋尘能够反映室内环境卫生状况以及各种刺激因子的暴露水平.动物实验研究表明,屋尘提取物既有Th2免疫佐剂效应,又有免疫保护效应,这取决于屋尘提取物暴露的持续时间和剂量.为进一步明确室内环境暴露与过敏性哮喘的关系并为早期防治提供更好的策略,文章分别从微生物成分与哮喘、屋尘提取物干预的哮喘动物模型、屋尘提取物对过敏性哮喘小鼠影响的激活路径等三个方面,综述屋尘提取物暴露对过敏性哮喘的免疫调节机制.     

Childhood asthma and the indoor environment

To investigate the influence of indoor air quality on respiratory health, a questionnaire-based study of 17,962 Canadian schoolchildren in kindergarten through grade 2 was carried out in 1988. The present report focuses on associations between several indoor environmental factors and childhood asthma. Increased reports of physician-diagnosed asthma were significantly associated (p less than 0.001) with exposure to environmental tobacco smoke (OR = 1.4), living in a damp home (OR = 1.5), the use of gas for cooking (OR = 2.0) and the use of a humidifier (OR = 1.7). Wheezing without a diagnosis of asthma also was associated (p less than 0.01) with environmental tobacco smoke (OR = 1.4, home dampness (OR = 1.6) and humidifier use (OR = 1.4), but not with gas cooking. Thus, several modifiable risk factors for respiratory illness may exist in Canadian homes. Further research is required to determine the nature of these cross-sectional observations.     

Direct and Indirect Exposure to Horse: Risk for Sensitization and Asthma

Most studies on the sensitization to horse allergens in populations without professional exposure have been carried out in geographical areas where the rate of horse ownership is high and horse riding is popular. Very few studies have been carried out in populations living in large urban areas. This gap in the literature probably reflects the widespread view that prevalence of horse-related allergy is low in urban populations because the latter are not regularly exposed to horses. On the contrary, we suggest that urban areas constitute a model useful to study potential modalities of exposure and sensitization to horse allergen by other routes of exposure than horse-riding. In this article, we describe the risks related to various modalities of exposure to horse allergen, clinical aspects of airway sensitization to horse allergens in patients living in urban areas, and non-occupational exposure to horse allergen. In addition, we illuminate some aspects related to dispersion of horse allergens from sources such as stables to indoor environments.     

Importance of mold allergy in asthma

Fungal exposure is hypothesized (controversially) to contribute to asthma development and to trigger symptoms in patients with asthma. The ubiquity of environmental fungal exposure makes a careful review of evidence essential. Evidence that exposure to high concentrations of fungal spores, antigens, or metabolites is associated with asthma development is limited. However, because mechanisms of asthma genesis are poorly understood, so too are the mechanisms of this potential association. This association is not proof of causality. Stronger evidence supports the hypothesis that fungal exposure triggers symptoms in asthmatic individuals. Proposed mechanisms have been tested and correlations between exposure and symptoms demonstrated. Though some correlations remain speculative, controlled studies could test such hypotheses. Because asthma is common and fungal exposure is ubiquitous, it is surprising that asthmatics don’t have more symptoms when exposed to fungi. Fortunately, symptoms are dose dependent, creating an opportunity to develop clinically effective interventions. Given the right guidance, even patients with severe asthma can create healthy indoor environments.     

Emerging Insights into the Occupational Mycobiome

Purpose of Review

The evolution of molecular-based methods over the last two decades has provided new approaches to identify and characterize fungal communities or “mycobiomes” at resolutions previously not possible using traditional hazard identification methods. The recent focus on fungal community assemblages within indoor environments has provided renewed insight into overlooked sources of fungal exposure. In occupational studies, internal transcribed spacer (ITS) region sequencing has recently been utilized in a variety of environments ranging from indoor office buildings to agricultural commodity and harvesting operations.

Recent Findings

Fungal communities identified in occupational environments have been primarily placed in the phylum Ascomycota and included classes typically identified using traditional fungal exposure methods such as the Eurotiomycetes, Dothideomycetes, Sordariomycetes, and Saccharomycetes. The phylum Basidiomycota has also been reported to be more prevalent than previously estimated and ITS region sequences have been primarily derived from the classes Agaricomycetes and Ustilaginomycetes. These studies have also resolved sequences placed in the Basidiomycota classes Tremellomycetes and Exobasidiomycetes that include environmental and endogenous yeast species.

Summary

These collective datasets have shown that occupational fungal exposures include a much broader diversity of fungi than once thought. Although the clinical implications for occupational allergy are an emerging field of research, establishing the mycobiome in occupational environments will be critical for future studies to determine the complete spectrum of worker exposures to fungal bioaerosols and their impact on worker health.

     

Indoor moisture and mold-related health problems

Moisture, microbial and in particular mold related indoor exposure and health problems in homes, offices, and public buildings (Kindergartens, schools, library, and hospitals) have been gaining recognition as one of the most common indoor environmental health issues. Proper recognition of microbial related health problems and the differential diagnosis of sick building syndrome (SBS) or building related illness (BRI) are important for early and effective exposure intervention, treatment, referral and prevention of more serious illness.     

Pets and cockroaches: two increasing causes of respiratory allergy in indoor environments. Characteristics of airways sensitization and prevention strategies

The increasing prevalence of allergic sensitization to indoor allergens such as dust mites, pets and cockroaches is the result of the changes in indoor environments induced by human activities. The Westernized lifestyle and the increasing time spent indoors determine a reduction in natural air ventilation and, consequently, higher levels of allergen concentrations and longer exposure to allergens. The major cat allergen Fel d 1 is carried by small-dimension particles (< 5 microm diameter) that readily become airborne and persist immodified for a long time. Fel d 1 must be considered a ubiquitous allergen because it has been found in indoor environments and even in public places where a cat has never been kept. Recent research has demonstrated that clothing of cat owners may contribute to the dispersal of Fel d 1 in cat-free environments. Therefore, washing Fel d 1-contaminated clothes should be considered a simple and effective method for removing this allergen from clothing and, consequently, reducing the risk of Fel d 1 dispersion. Cockroach allergens constitute another important cause of environment-related respiratory allergy and may trigger asthma exacerbations in sensitized individuals. In the prevention of cockroach allergy, the use of chemical agents associated with an intensive vacuum cleaning of indoor environments is an important tool in removing cockroach material containing allergenic proteins. Early recognition of allergy-predisposed babies, monitoring indoor allergens and adequate strategies of allergen avoidance are likely to be important means for reducing the prevalence of bronchial asthma.     

微生物暴露与支气管哮喘的关系

支气管哮喘（简称哮喘）尤其是儿童哮喘的发病率在全球范围有明显升高。而在农场长大的儿童哮喘发病率较低。哮喘发病率的升高与卫生条件改善、家庭规模缩小和微生物暴露尤其是个体早期微生物暴露机会减少有关,其降低了机体接受“免疫训练”的机会,即“卫生学说”,近期有学者建议改为“早期免疫刺激假说”。该文主要介绍早期微生物及微生物组分暴露与哮喘的关系的作用机制进展,早期微生物暴露可能是潜在的预防哮喘的新途径。     

Home and school environmental assessment and remediation

Children spend a considerable portion of their time indoors. Therefore, homes and schools are an important source of allergen exposure. Chronic exposure to the major indoor allergens can lead to allergic sensitization and provoke allergic symptoms in children. Environmental assessment is crucial for the identification and quantification of such allergens in indoor spaces. Reduction of allergen exposure below sensitization and symptom thresholds is possible with various remediation techniques. This article reviews and discusses evidence for the assessment and remediation of indoor allergens commonly found in homes and schools. A literature review was performed using the PubMed database for English-language articles published between January 1, 1980, and February 2009. Additional information was obtained from a review of recent textbooks and one professional society’s webpage.     

Studies of Sick Building Syndrome. IV. Mycotoxicosis

There has been increasing public attention to the potential health risks of mold exposure, particularly in wet buildings. A variety of molds has been isolated from both damaged homes and businesses, including agents that secrete toxigenic materials. One area that is attracting particular notice is the relative toxigenic potential of mycotoxins. Although exposure to molds can produce significant mucosal irritation, there are very few data to suggest long-term ill effects. More importantly, there is no evidence in humans that mold exposure leads to nonmucosal pathology. In fact, many of the data on toxigenic molds are derived from animal toxicity studies, and these are based primarily on ingestion. Although every attempt should be made to improve the quality of indoor air, including avoidance of molds, the human illnesses attributed to fungal exposure are, with the exception of invasive infections and mold allergy, relatively rare. In this review we discuss selected aspects of the microbiology of mycotoxin-producing molds and their potential role in human immunopathology with respect to wet building environments.     

Air measurements of dusts, chemicals, and fumes.

Estimates of exposure in the workplace or in indoor environments begin with the actual sampling and analysis of the airborne contaminant or rely on a reconstruction of past exposures in the workplace. Direct-reading portable field instruments are being used to supplement laboratory-based analytical methods. The lowering of the OSHA permissible exposure limits and the rise of indoor air pollution concerns indicate the need for more innovative methods for detecting lung irritants and pathogens.