High-resolution mass spectrometry identifies delayed biomarkers for improved precision in acetaminophen/paracetamol human biomonitoring.

Paracetamol/acetaminophen (N-acetyl-p-aminophenol, APAP) is a top selling analgesic used in more than 600 prescription and non-prescription pharmaceuticals. To study efficiently some of the potential undesirable effects associated with increasing APAP consumption (e.g., developmental disorders, drug-induced liver injury), there is a need to improve current APAP biomonitoring methods that are limited by APAP short half-life. Here, we demonstrate using high-resolution mass spectrometry (HRMS) in several human studies that APAP thiomethyl metabolite conjugates (S-methyl-3-thioacetaminophen sulfate and S-methyl-3-thioacetaminophen sulphoxide sulfate) are stable biomarkers with delayed excretion rates compared to conventional APAP metabolites, that could provide a more reliable history of APAP ingestion in epidemiological studies. We also show that these biomarkers could serve as relevant clinical markers to diagnose APAP acute intoxication in overdosed patients, when free APAP have nearly disappeared from blood. Using in vitro liver models (HepaRG cells and primary human hepatocytes), we then confirm that these thiomethyl metabolites are directly linked to the toxic N-acetyl-p-benzoquinone imine (NAPQI) elimination, and produced via an overlooked pathway called the thiomethyl shunt pathway. Further studies will be needed to determine whether the production of the reactive hepatotoxic NAPQI metabolites is currently underestimated in human. Nevertheless, these biomarkers could already serve to improve APAP human biomonitoring, and investigate, for instance, inter-individual variability in NAPQI production to study underlying causes involved in APAP-induced hepatotoxicity. Overall, our findings demonstrate the potential of exposomics-based HRMS approach to advance towards a better precision for human biomonitoring.

Early exposure to farm dust in an allergic airway inflammation rabbit model: Does it affect bronchial and cough hyperresponsiveness?

INTRODUCTION: Over the past 50 years, the prevalence of allergic respiratory diseases has been increasing. The Hygiene hypothesis explains this progression by the decrease in the bio-diversity of early microbial exposure. This study aims to evaluate the effect of early-life farm exposure on airway hyperresponsiveness and cough hypersensitivity in an allergic airway inflammation rabbit model. METHOD: A specific environment was applied to pregnant rabbits and their offspring until six weeks after birth. Rabbits were housed in a pathogen-free zone for the control group and a calf barn for the farm group. At the end of the specific environmental exposure, both groups were then housed in a conventional zone and then sensitized to ovalbumin. Ten days after sensitization, the rabbit pups received ovalbumin aerosols to provoke airway inflammation. Sensitization to ovalbumin was assessed by specific IgE assay. Cough sensitivity was assessed by mechanical stimulation of the trachea, and bronchial reactivity was assessed by methacholine challenge. The farm environment was characterized by endotoxin measurement. RESULTS: A total of 38 rabbit pups were included (18 in the farm group). Endotoxin levels in the farm environment varied from 30 to 1854 EU.m-3. There was no significant difference in specific IgE values to ovalbumin (p = 0.826) between the two groups. The mechanical threshold to elicit a cough did not differ between the two groups (p = 0.492). There was no difference in the number of cough (p = 0.270) or the intensity of ventilatory responses (p = 0.735). After adjusting for age and weight, there was no difference in respiratory resistance before and after methacholine challenge. CONCLUSION: Early exposure to the calf barn did not affect cough sensitivity or bronchial reactivity in ovalbumin-sensitized rabbits. These results suggest that not all farm environments protect against asthma and atopy. Continuous exposure to several sources of microbial diversity is probably needed.

Indoor Carbon Dioxide, Fine Particulate Matter and Total Volatile Organic Compounds in Private Healthcare and Elderly Care Facilities.

Poor indoor air quality can have adverse effects on human health, especially in susceptible populations. The aim of this study was to measure the concentrations of dioxide carbon (CO2), fine particulate matter (PM2.5) and total volatile organic compounds (TVOCs) in situ in private healthcare and elderly care facilities. These pollutants were continuously measured in two rooms of six private healthcare facilities (general practitioner's offices, dental offices and pharmacies) and four elderly care facilities (nursing homes) in two French urban areas during two seasons: summer and winter. The mean CO2 concentrations ranged from 764 ± 443 ppm in dental offices to 624 ± 198 ppm in elderly care facilities. The mean PM2.5 concentrations ranged from 13.4 ± 14.4 µg/m3 in dental offices to 5.7 ± 4.8 µg/m3 in general practitioner offices. The mean TVOC concentrations ranged from 700 ± 641 ppb in dental offices to 143 ± 239 ppb in general practitioner offices. Dental offices presented higher levels of indoor air pollutants, associated with the dental activities. Increasing the ventilation of these facilities by opening a window is probably an appropriate method for reducing pollutant concentrations and maintaining good indoor air quality.

Quantitative Health Risk Assessment of the Chronic Inhalation of Chemical Compounds in Healthcare and Elderly Care Facilities.

Previous studies have described the chemical pollution in indoor air of healthcare and care facilities. From these studies, the main objective of this work was to conduct a quantitative health risk assessment of the chronic inhalation of chemical compounds by workers in healthcare and elderly care facilities (hospitals, dental and general practitioner offices, pharmacies and nursing homes). The molecules of interest were 36 volatile and 13 semi-volatile organic compounds. Several professional exposure scenarios were developed in these facilities. The likelihood and severity of side effects that could occur were assessed by calculating the hazard quotient for deterministic effects, and the excess lifetime cancer risk for stochastic effects. No hazard quotient was greater than 1. Three compounds had a hazard quotient above 0.1: 2-ethyl-1-hexanol in dental and general practitioner offices, ethylbenzene and acetone in dental offices. Only formaldehyde presented an excess lifetime cancer risk greater than 1 × 10-5 in dental and general practitioner offices (maximum value of 3.8 × 10-5 for general practitioners). The health risk for chronic inhalation of most compounds investigated did not appear to be of concern. Some values tend to approach the acceptability thresholds justifying a reflection on the implementation of corrective actions such as the installation of ventilation systems.

Metagenomic Characterization of Indoor Dust Bacterial and Fungal Microbiota in Homes of Asthma and Non-asthma Patients Using Next Generation Sequencing.

BACKGROUND: The exposure of house occupants to indoor air pollutants has increased in recent decades. Among microbiological contaminants, bacterial and fungal aerosols remain poorly studied and the debate on the impact of these aerosols on respiratory health is still open. This study aimed to assess the diversity of indoor microbial communities in relationship with the health of occupants. METHODS: Measurements were taken from dwellings of 2 cohorts in Brittany (France), one with children without any pathology and the other with children and adults with asthma. Thirty dust samples were analyzed by next generation sequencing with a 16S and 18S targeted metagenomics approach. Analysis of sequencing data was performed using qiime 2, and univariate and multivariate statistical analysis using R software and phyloseq package. RESULTS: A total of 2,637 prokaryotic (589 at genus level) and 2,153 eukaryotic taxa were identified (856 fungal taxa (39%) and 573 metazoa (26%)). The four main bacterial phyla were identified: Proteobacteria (53%), Firmicutes (27%), Actinobacteria (11%), Bacteroidetes (8%). Among Fungi, only 136 taxa were identified at genus level. Three main fungal phyla were identified: Ascomycota (84%), Basidiomycota (12%) and Mucoromycota (3%). No bacterial nor fungal phyla were significantly associated with asthma versus control group. A significant over representation in control group versus asthma was observed for Christensenellaceae family (p-value = 0.0015, adj. p-value = 0.033). Besides, a trend for over representation in control group was observed with Dermabacteraceae family (p-value = 0.0002, adj. p-value = 0.815). CONCLUSIONS: Our findings provide evidence that dust samples harbor a high diversity of human-associated bacteria and fungi. Molecular methods such as next generation sequencing are reliable tools for identifying and tracking the bacterial and fungal diversity in dust samples, a less easy strategy for the detection of eukaryotes at least using18S metagenomics approach. This study showed that the detection of some bacteria might be associated to indoor air of asthmatic patients. Regarding fungi, a higher number of samples and sequencing with more depth could allow reaching significant signatures.

Asthma and Indoor Environment: Usefulness of a Global Allergen Avoidance Method on Asthma Control and Exposure to Molds.

The usefulness and feasibility of a global allergens avoidance method with counselors visiting patients' home for allergens measures and adapted advices were prospectively evaluated through asthma control and environment evaluation. Twenty seven patients were prospectively included and compared to a cohort of 30 control patients. The level of control of asthma at inclusion and after 1 year was evaluated by the clinical signs, the evolution of the FEV1, and the healthcare use. Environmental measurements included the fungal load of 5 surfaces of the dwellings and the evaluation of moisture. A significant clinical improvement in the population that benefited from the home counselors visit was observed compared to the baseline (p < 0.0001), as well as a decreased number of hospitalizations for asthma and of the consumption of anti-asthma drugs (p < 0.01). Dampness markers slightly improved with an improvement of the fungal loads in two-third of the dwellings.

Emissions of VOCs, SVOCs, and mold during the construction process: Contribution to indoor air quality and future occupants' exposure.

Building materials and human activities are important sources of contamination indoors, but little information is available regarding contamination during construction process which could persist during the whole life of buildings. In this study, six construction stages on two construction sites were investigated regarding the emissions of 43 volatile organic compounds (VOCs), 46 semi-volatile organic compounds (SVOCs), and the presence of 4 genera of mold. Results show that the future indoor air quality does not only depend on the emissions of each building product but that it is also closely related to the whole implementation process. Mold spore measurements can reach 1400 CFU/m3 , which is particularly high compared with the concentrations usually measured in indoor environments. Relatively low concentrations of VOCs were observed, in relation to the use of low emissive materials. Among SVOCs analyzed, some phthalates, permethrin, and hydrocarbons were found in significant concentrations upon the delivery of building as well as triclosan, suspected to be endocrine disruptor, and yet prohibited in the treatment of materials and construction since 2014. As some regulations exist for VOC emissions, it is necessary to implement them for SVOCs due to their toxicity.

Adenovirus behavior in air handling unit fiberglass filters.

Viral aerosols can lead to respiratory viral infections with high infectivity. About 90% of people's time is spent in closed environments. A few studies have pointed out that the ventilation systems in air handling units (AHUs) that treat and transmit a new synthetic clean and conditioned environment can also spread and transport viral particles in buildings. The aim of this work is to study the characterization of adenovirus, a DNA non-enveloped respiratory virus, on the F7 fiberglass filter used in AHUs. In this study, an experimental setup simulating an AHU was used. The SYBR® QPCR, Electrical Low-Pressure Impactor (ELPI™) and Scanning Mobility Particle Sizer (SMPS™) were used to detect, measure and characterize the aerosolized adenovirus solution. The characterization results showed that the nebulized adenovirus could be aerosolized in different forms associated or not with cell debris and proteins. The quantification and level of infectivity of adenovirus demonstrated that viruses passed through filters and remained infectious up- and downstream of the system during the 25 min of aerosolization. This study showed that AHUs should be considered an indoor source of viral contamination.

Indoor air quality in two French hospitals: Measurement of chemical and microbiological contaminants.

In addition to being influenced by the environment, the indoor air pollution in hospitals may be associated with specific compounds emitted from various products used, health care activities and building materials. This study has enabled assessment of the chemical and microbiological concentrations of indoor air in two French hospitals. Based on an integrated approach, the methodology defined aims to measure concentrations of a wide range of chemical compounds (>50 volatile and semi-volatile organic compounds), particle concentrations (PM10 and PM2.5), microorganisms (fungi, bacteria and viruses) and ambient parameters (temperature, relative humidity, pressure and carbon dioxide). Chemical and microbiological air concentrations were measured during two campaigns (winter and summer) and across seven rooms (for spatial variability). The results have shown that indoor air contains a complex mixture of chemical, physical and microbiological compounds. Concentrations in the same order of magnitude were found in both hospitals. Compared to dwelling indoor air, our study shows low, at least equivalent, contamination for non-hospital specific parameters (aldehydes, limonene, phthalates, aromatic hydrocarbons), which is related to ventilation efficiency. Chemical compounds retrieved at the highest concentration and frequencies are due to healthcare activities, for example alcohol - most commonly ethanol - and hand rubbing (median concentration: ethanol 245.7 µg/m3 and isopropanol 13.6 µg/m3); toluene and staining in parasitology (highest median concentration in Nancy laboratory: 2.1 µg/m3)).

Granulometry, microbial composition and biological activity of dusts collected in French dairy farms.

BACKGROUND: Dairy working increases the prevalence of lower airway respiratory diseases, especially COPD and asthma. Epidemiological studies have reported that chronic inhalation of organic dusts released during specific daily tasks could represent a major risk factor for development of these pathologies in dairy workers. Knowledge on size, nature and biological activity of such organic dusts remain however limited. OBJECTIVE: To compare size distribution, microbial composition and cellular effects of dusts liberated by the spreading of straw bedding in five French dairy farms located in Brittany. RESULTS: Mechanized distribution of straw bedding generated a cloud of inhalable dusts in the five dairy farms' barns. Thoracic particles having a 3-7.5µm size constituted 58.9-68.3% of these dusts. Analyses of thoracic dusts by next generation sequencing showed that the microbial dust composition differed between the five French farms, although Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria represent more than 97.5% of the bacterial phyla detected in each sample. Several bacteria genera comprising of human pathogenic species, such as Pseudomonas, Staphylococcus, Thermoactinomyces or Saccharopolyspora were identified. Cladosporium and Alternaria fungal genera, which are potent environmental determinants of respiratory symptoms, were detected in dusts collected in the five farms and their levels reached 15.5-51.1% and 9-24.7% of assignable fungal sequences in each sample, respectively. Finally, all dust samples significantly and strongly increased the expression of the pro-inflammatory TNF-α, IL-1ß, IL-6 and IL-8 cytokines at both mRNA and protein levels in human monocyte-derived macrophages. Their effects were dose-dependent and detectable from 1µg/ml. The intensity of the macrophage responses however differed according to the samples. CONCLUSIONS: Our results strengthen the hypothesis that organic dusts released during the distribution of straw bedding are mainly constituted of thoracic particles which are small enough to deposit on lower bronchial epithelium of dairy farmers and induce inflammation.

The Fate of Mengovirus on Fiberglass Filter of Air Handling Units.

One of the most important topics that occupy public health problems is the air quality. That is the reason why mechanical ventilation and air handling units (AHU) were imposed by the different governments in the collective or individual buildings. Many buildings create an artificial climate using heating, ventilation, and air-conditioning systems. Among the existing aerosols in the indoor air, we can distinguish the bioaerosol with biological nature such as bacteria, viruses, and fungi. Respiratory viral infections are a major public health issue because they are usually highly infective. We spend about 90% of our time in closed environments such as homes, workplaces, or transport. Some studies have shown that AHU contribute to the spread and transport of viral particles within buildings. The aim of this work is to study the characterization of viral bioaerosols in indoor environments and to understand the fate of mengovirus eukaryote RNA virus on glass fiber filter F7 used in AHU. In this study, a set-up close to reality of AHU system was used. The mengovirus aerosolized was characterized and measured with the electrical low pressure impact and the scanner mobility particle size and detected with RT-qPCR. The results about quantification and the level of infectivity of mengovirus on the filter and in the biosampler showed that mengovirus can pass through the filter and remain infectious upstream and downstream the system. Regarding the virus infectivity on the filter under a constant air flow, mengovirus was remained infectious during 10 h after aerosolization.

Home Environmental Interventions for the Prevention or Control of Allergic and Respiratory Diseases: What Really Works.

Home health care workers interventions have been implemented in western countries to improve health status of patients with respiratory diseases especially asthma and allergic illnesses. Twenty-six controlled studies dealing with prevention and control of these diseases through home environmental interventions were reviewed. After a comprehensive description of the characteristics of these studies, the effectiveness of each intervention was then evaluated in terms of participants' compliance with the intervention program, improvement of quality of the indoor environment, and finally improvement of health outcomes, in detailed tables. Limitations and biases of the studies are also discussed. Overall, this review aims at giving a toolbox for home health care workers to target the most appropriate measures to improve health status of the patient depending on his and/or her environment and disease. Only a case-by-case approach with achievable measures will warrant the efficacy of home interventions. This review will also provide to the research community a tool to better identify targets to focus in future evaluation studies of home health care workers action.

Concentration and determinants of molds and allergens in indoor air and house dust of French dwellings.

Molds and allergens are common indoor biocontaminants. The aims of this study were to assess the concentrations of common molds in indoor air and floor dust and the concentrations of house dust mite, cat and dog allergens in mattress dust in French dwellings, and to assess predictors of these concentrations. A sample of 150 houses in Brittany (western France) was investigated. Airborne Cladosporium and Penicillium were detected in more than 90% of the dwellings, Aspergillus in 46% and Alternaria in only 6% of the housings. Regarding floor dust samples, Cladosporium and Penicillium were detected in 92 and 80% of the housings respectively, Aspergillus in 49% and Alternaria in 14%. House dust mite allergens Der p1 and Der f1 were detected in 90% and 77% of the mattress dust samples respectively and Can f1 and Fel d1 in 37% and 89% of the homes. Airborne and dustborne mold concentrations, although not statistically correlated (except for Aspergillus) shared most of their predictors. Multivariate linear models for mold levels, explaining up to 62% of the variability, showed an influence of the season, of the age of the dwelling, of aeration habits, presence of pets, smoking, signals of dampness, temperature and relative humidity. Allergens in the dust of the mattress were strongly related to the presence of pets and cleaning practices of bedsheets, these factors accounting for 60% of the variability. This study highlights ubiquitous contamination by molds and underlines complex interaction between outdoor and indoor sources and factors.

Microbial contamination detection in water resources: interest of current optical methods, trends and needs in the context of climate change.

Microbial pollution in aquatic environments is one of the crucial issues with regard to the sanitary state of water bodies used for drinking water supply, recreational activities and harvesting seafood due to a potential contamination by pathogenic bacteria, protozoa or viruses. To address this risk, microbial contamination monitoring is usually assessed by turbidity measurements performed at drinking water plants. Some recent studies have shown significant correlations of microbial contamination with the risk of endemic gastroenteresis. However the relevance of turbidimetry may be limited since the presence of colloids in water creates interferences with the nephelometric response. Thus there is a need for a more relevant, simple and fast indicator for microbial contamination detection in water, especially in the perspective of climate change with the increase of heavy rainfall events. This review focuses on the one hand on sources, fate and behavior of microorganisms in water and factors influencing pathogens' presence, transportation and mobilization, and on the second hand, on the existing optical methods used for monitoring microbiological risks. Finally, this paper proposes new ways of research.

Indoor fungal contamination: health risks and measurement methods in hospitals, homes and workplaces.

Indoor fungal contamination has been associated with a wide range of adverse health effects, including infectious diseases, toxic effects and allergies. The diversity of fungi contributes to the complex role that they play in indoor environments and human diseases. Molds have a major impact on public health, and can cause different consequences in hospitals, homes and workplaces. This review presents the methods used to assess fungal contamination in these various environments, and discusses advantages and disadvantages for each method in consideration with different health risks. Air, dust and surface sampling strategies are compared, as well as the limits of various methods are used to detect and quantify fungal particles and fungal compounds. In addition to conventional microscopic and culture approaches, more recent chemical, immunoassay and polymerase chain reaction (PCR)-based methods are described. This article also identifies common needs for future multidisciplinary research and development projects in this field, with specific interests on viable fungi and fungal fragment detections. The determination of fungal load and the detection of species in environmental samples greatly depend on the strategy of sampling and analysis. Quantitative PCR was found useful to identify associations between specific fungi and common diseases. The next-generation sequencing methods may afford new perspectives in this area.

Factors associated with post-seasonal serological titer and risk factors for infection with the pandemic A/H1N1 virus in the French general population.

The CoPanFlu-France cohort of households was set up in 2009 to study the risk factors for infection by the pandemic influenza virus (H1N1pdm) in the French general population. The authors developed an integrative data-driven approach to identify individual, collective and environmental factors associated with the post-seasonal serological H1N1pdm geometric mean titer, and derived a nested case-control analysis to identify risk factors for infection during the first season. This analysis included 1377 subjects (601 households). The GMT for the general population was 47.1 (95% confidence interval (CI): 45.1, 49.2). According to a multivariable analysis, pandemic vaccination, seasonal vaccination in 2009, recent history of influenza-like illness, asthma, chronic obstructive pulmonary disease, social contacts at school and use of public transports by the local population were associated with a higher GMT, whereas history of smoking was associated with a lower GMT. Additionally, young age at inclusion and risk perception of exposure to the virus at work were identified as possible risk factors, whereas presence of an air humidifier in the living room was a possible protective factor. These findings will be interpreted in light of the longitudinal analyses of this ongoing cohort.

Possible application of the Environmental Relative Moldiness Index in France: a pilot study in Brittany.

Our goal was to determine if the US Environmental Relative Moldiness Index (ERMI) scale might have application in France. Twenty homes in Brittany, north western region of France were classified by inspection as "Moldy" or "Non-Moldy". Dust and air samples were collected (MiTest sampler or Coriolis sampler, respectively) from each home and analyzed by quantitative polymerase chain reaction (QPCR) for the 36 fungi that make-up the ERMI. Inspection and ERMI values provided a consistent assessment for 90% of the homes. Two homes originally classified as "Non-Moldy" were found to fit better into the "Moldy" category based on the QPCR analysis and the ERMI. Dust and air samples analyzed by QPCR provided similar fungal contamination assessments. In conclusion, a metric like the ERMI describes mold burdens in homes on a continuum, as opposed to the frequently used dichotomous approach (moldy vs. non-moldy). Although a larger, random national sampling of French homes is needed, these results suggest that these same 36 fungi may be useful in creating an ERMI for France.

Correlation between Environmental Relative Moldiness Index (ERMI) values in French dwellings and other measures of fungal contamination.

The Environmental Relative Moldiness Index (ERMI) is a DNA-based metric developed to describe the fungal contamination in US dwellings. Our goal was to determine if the ERMI values in dwellings in north western France were correlated with other measures of fungal contamination. Dust and air samples were obtained from 40 dwellings and analyzed by quantitative PCR and/or by culturing. These dwellings were also inspected and the amount of visible fungal growth estimated in m(2). The ERMI values in these dwellings ranged from -2.7 to 28.8 and the fungal contamination estimates ranged from 0 to 20 m(2). The 40 dwellings were divided into those with a low (<6) or high (>8) ERMI values (n=20 in each). The average ERMI value was 15.70 for the high ERMI compared to 2.68 for the low ERMI dwellings. ERMI values were correlated (significant Kendall's tau values) with concentrations of fungi in air samples analyzed by QPCR or culturing. ERMI values were also correlated (significant Kendall's tau values) with the visible estimates of fungal contamination. Older dwellings were more likely to have higher ERMI values. These results suggest that the ERMI dust sample, which is quick and easy to collect, may be useful in making decisions about reducing fungal exposures in homes.

Integrative study of pandemic A/H1N1 influenza infections: design and methods of the CoPanFlu-France cohort.

BACKGROUND: The risk of influenza infection depends on biological characteristics, individual or collective behaviors and the environmental context. The Cohorts for Pandemic Influenza (CoPanFlu) France study was set up in 2009 after the identification of the novel swine-origin A/H1N1 pandemic influenza virus. This cohort of 601 households (1450 subjects) representative for the general population aims at using an integrative approach to study the risk and characteristics of influenza infection as a complex combination of data collected from questionnaires regarding sociodemographic, medical, behavioral characteristics of subjects and indoor environment, using biological samples or environmental databases. METHODS/DESIGN: Households were included between December 2009 and July 2010. The design of this study relies on systematic follow-up visits between influenza seasons and additional visits during influenza seasons, when an influenza-like illness is detected in a household via an active surveillance system. During systematic visits, a nurse collects individual and environmental data on questionnaires and obtains blood samples from all members of the household. When an influenza-like-illness is detected, a nurse visits the household three times during the 12 following days, and collects data on questionnaires regarding exposure and symptoms, and biological samples (including nasal swabs) from all subjects in the household. The end of the follow-up period is expected in fall 2012. DISCUSSION: The large amount of data collected throughout the follow-up will permit a multidisciplinary study of influenza infections. Additional data is being collected and analyzed in this ongoing cohort. The longitudinal analysis of these households will permit integrative analyses of complex phenomena such as individual, collective and environmental risk factors of infection, routes of transmission, or determinants of the immune response to infection or vaccination.

Indoor environment and children's health: recent developments in chemical, biological, physical and social aspects.

Much research is being carried out into indoor exposure to harmful agents. This review focused on the impact on children's health, taking a broad approach to the indoor environment and including chemical, microbial, physical and social aspects. Papers published from 2006 onwards were reviewed, with regards to scientific context. Most of publications dealt with chemical exposure. Apart from the ongoing issue of combustion by-products, most of these papers concerned semi volatile organic compounds (such as phthalates). These may be associated with neurotoxic, reprotoxic or respiratory effects and may, therefore, be of particular interest so far as children are concerned. In a lesser extent, volatile organic compounds (such as aldehydes) that have mainly respiratory effects are still studied. Assessing exposure to metals is still of concern, with increasing interest in bioaccessibility. Most of the papers on microbial exposure focused on respiratory tract infections, especially asthma linked to allergens and bio-aerosols. Physical exposure includes noise and electromagnetic fields, and articles dealt with the auditory and non auditory effects of noise. Articles on radiofrequency electromagnetic fields mainly concerned questions about non-thermal effects and papers on extremely low-frequency magnetic fields focused on the characterization of exposure. The impact of the indoor environment on children's health cannot be assessed merely by considering the effect of these different types of exposure: this review highlights new findings and also discusses the interactions between agents in indoor environments and also with social aspects.