Effect of formaldehyde on asthmatic response to inhaled allergen challenge

A Comprehensive Literature Review on the Effects of Formaldehyde on the Upper Respiratory Tract

Prolonged exposure to indoor air pollutants at high concentrations can have adverse health effects on the respiratory system of individuals who spend most of their time indoors. Formaldehyde (FA) is a common indoor air pollutant because of its extensive use in household products such as cleaners, floorings, and furnishings. As a chemical, FA is highly water soluble and reactive. When its airborne form is inhaled, it is mainly absorbed in the upper airways. FA has been extensively studied for its carcinogenic effects, but it can also cause inflammation in the upper airways. The objective of the current review was to assess the secondary effects of such inflammation and how it can contribute to an increased risk for upper respiratory infections, which are mostly caused by viruses. A rigorous literature review was conducted through gathering, reading, and analyzing relevant literature, including peer-reviewed articles published after 1990 and seminal literature regardless of publication date. Findings from the review provide a greater understanding of the outcomes of FA exposure, the potential accumulative damage to the upper respiratory tract, and the associated increased risk for acute infections of the upper respiratory tract. This information can help in the development and enforcement of stricter regulations for furniture and building materials for household-related products to limit exposure to indoor pollutants such as FA.

Environmental Engineering Applications of Electronic Nose Systems Based on MOX Gas Sensors

Nowadays, the electronic nose (e-nose) has gained a huge amount of attention due to its ability to detect and differentiate mixtures of various gases and odors using a limited number of sensors. Its applications in the environmental fields include analysis of the parameters for environmental control, process control, and confirming the efficiency of the odor-control systems. The e-nose has been developed by mimicking the olfactory system of mammals. This paper investigates e-noses and their sensors for the detection of environmental contaminants. Among different types of gas chemical sensors, metal oxide semiconductor sensors (MOXs) can be used for the detection of volatile compounds in air at ppm and sub-ppm levels. In this regard, the advantages and disadvantages of MOX sensors and the solutions to solve the problems arising upon these sensors' applications are addressed, and the research works in the field of environmental contamination monitoring are overviewed. These studies have revealed the suitability of e-noses for most of the reported applications, especially when the tools were specifically developed for that application, e.g., in the facilities of water and wastewater management systems. As a general rule, the literature review discusses the aspects related to various applications as well as the development of effective solutions. However, the main limitation in the expansion of the use of e-noses as an environmental monitoring tool is their complexity and lack of specific standards, which can be corrected through appropriate data processing methods applications.

Formaldehyde exposure induces differentiation of regulatory T cells via the NFAT-mediated T cell receptor signalling pathway in Yucatan minipigs

The use of minipigs (Sus scrofa) as a platform for toxicological and pharmacological research is well established. In the present study, we investigated the effect of formaldehyde (FA) exposure on helper T cell-mediated splenic immune responses in Yucatan minipigs. The minipigs were exposed to different inhaled concentrations of FA (0, 2.16, 4.62, or 10.48 mg/m³) for a period of 2 weeks. Immune responses elicited by exposure to FA were determined by assessing physiological parameters, mRNA expression, and cytokine production. Additionally, the distribution of helper T cells and regulatory T (Treg) cells and expression of NFAT families, which are well-known T cell receptor signalling proteins associated with regulatory T cell development, were evaluated. Exposure to FA suppressed the expression of genes associated with Th1 and Th2 cells in minipigs in a concentration-dependent manner. The subsequent production of cytokines also declined post-FA exposure. Furthermore, exposure to FA induced the differentiation of CD4⁺ Foxp3⁺ Treg cells with divergent expression levels of NFAT1 and NFAT2. These results indicated that exposure to FA increased the Treg cell population via the NFAT-mediated T cell receptor signalling pathway, leading to suppression of effector T cell activity with a decline in T cell-related cytokine production.

Harmful Effect of Indoor Formaldehyde on Atopic Dermatitis in Children: A Longitudinal Study

Purpose

Evidence supporting a link between indoor formaldehyde exposure and atopic dermatitis (AD) in humans is limited. The purpose of this longitudinal study was to investigate whether AD symptoms in children could be affected by indoor formaldehyde levels in ordinary households.

Methods

Fifty-five children with moderate-to-severe AD aged under 18 years were enrolled as a panel. They were followed up from February 2019 through February 2020. Indoor formaldehyde levels of patients' houses and their AD symptoms were repeatedly measured on a daily basis. The generalized linear mixed model was utilized for statistical analysis. Subdivision analysis was performed by stratifying patients by sex, body mass index, presence of parental allergy, and indoor environments including mold/dampness, temperature, and relative humidity (RH).

Results

A total of 4,789 person-days of AD symptom data were collected. The average concentration of formaldehyde was 13.6 ± 16.4 ppb, with the highest value found in spring (18.1 ± 20.6 ppb). Higher levels of formaldehyde were observed when there was parental smoking, increased indoor temperature over 25.5°C, or RH over 60% (P < 0.0001). When the effect size was compared between each season after controlling for ambient particulate matter, temperature, and RH, an increase in 10 ppb of formaldehyde increased AD symptoms by 79.2% (95% confidence interval [CI], 19.6–168.4) in spring and by 39.9% (95% CI, 14.3–71.2) in summer. AD symptoms in children aged 6−18 years appeared to increase significantly, whereas there was no significant increase in children under 6 years. When indoor temperature was over 25.5°C, an increase in formaldehyde by 10 ppb increased AD symptoms by 17.8% (95% CI, 3.9–33.6).

Conclusions

Indoor formaldehyde can exacerbate AD symptom in children with moderate-to-severe AD, particularly in spring and summer, even at allowable levels. Thus, minimizing exposure to indoor formaldehyde may be needed for the proper management of AD in children.

Indoor air pollution, physical and comfort parameters related to schoolchildren's health: Data from the European SINPHONIE study

Substantial knowledge is available on the association of the indoor school environment and its effect among schoolchildren. In the same context, the SINPHONIE (School indoor pollution and health: Observatory network in Europe) conducted a study to collect data and determine the distribution of several indoor air pollutants (IAPs), physical and thermal parameters and their association with eye, skin, upper-, lower respiratory and systemic disorder symptoms during the previous three months. Finally, data from 115 schools in 54 European cities from 23 countries were collected and included 5175 schoolchildren using a harmonized and standardized protocol. The association between exposures and the health outcomes were examined using logistic regression models on the environmental stressors assessed in classroom while adjusting for several confounding factors; a VOC (volatile organic compound) score defined as the sum of the number of pollutants to which the children were highly exposed (concentration > median of the distribution) in classroom was also introduced to evaluate the multiexposure - outcome association. Schoolchildren while adjusting for several confounding factors. Schoolchildren exposed to above or equal median concentration of PM_2.5, benzene, limonene_, ozone and radon were at significantly higher odds of suffering from upper, lower airways, eye and systemic disorders. Increased odds were also observed for any symptom (sick school syndrome) among schoolchildren exposed to concentrations of limonene and ozone above median values. Furthermore, the risks for upper and lower airways and systemic disorders significantly increased with the VOCs score. Results also showed that increased ventilation rate was significantly associated with decreased odds of suffering from eye and skin disorders whereas similar association was observed between temperature and upper airways symptoms. The present study provides evidence that exposure to IAPs in schools is associated with various health problems in children. Further investigations are needed to confirm our findings.

Formaldehyde exposure induces regulatory T cell-mediated immunosuppression via calcineurin-NFAT signalling pathway

In this study, we investigated the effects of Formaldehyde (FA) exposure on splenic immune responses wherein helper T cells become activated and differentiate into effector T and regulatory T cells. BALB/c mice were exposed to two FA concentrations (1.38 mg/m3 and 5.36 mg/m3) for 4 h/day and 5 days/week for 2 weeks. FA-induced immune responses were examined by the production of cytokines, expression of mRNAs, and distributions of helper T cells and regulatory T cells. Moreover, expression of calcineurin and NFATs, regulatory T cell-related signalling proteins, were evaluated. FA exposure suppressed Th2-, Th1-, and Th17-related splenic cytokines in a dose-dependent manner. mRNA expression of splenic cytokines was also decreased by FA exposure, which correlated with decreased cytokine expression. In parallel, FA exposure promoted T cell differentiation into regulatory T cells in a dose-dependent manner supported by the expression of calcineurin and NFAT1. Taken together, our results indicated that FA exposure increases the number of regulatory T cells via calcineurin-NFAT signalling, thereby leading to effector T cell activity suppression with decreased T cell-related cytokine secretion and mRNA expression. These findings provide insight into the mechanisms underlying the adverse effects of FA and accordingly have general implications for human health, particularly in occupational settings.

Exposure to both formaldehyde and high relative humidity exacerbates allergic asthma by activating the TRPV4-p38 MAPK pathway in Balb/c mice

Some studies have indicated that formaldehyde, a ubiquitous environmental pollutant, can induce or aggravate allergic asthma. Epidemiological studies have also shown that the relative humidity indoors may be an independent and a key factor associated with the aggravation of allergic asthma. However, the synergy of humidity and formaldehyde on allergic asthma and the mechanism underlying this effect remain largely unknown. In this study, we aim to determine the effect of high relative humidity and/or formaldehyde exposure on allergic asthma and explore the underlying mechanisms. Male Balb/c mice were modeled with ovalbumin (OVA) and exposure to 0.5 mg/m³ formaldehyde and/or different relative humidity (60%/75%/90%). Histopathological changes, pulmonary function, Th1/Th2 balance, the status of mucus hypersecretion and the levels of inflammatory factors were detected to assess the exacerbation of allergic asthma. The levels of the transient receptor potential vanilloid 4 (TRPV4), calcium ion and the activation of p38 mitogen-activated protein kinases (p38 MAPK) were detected to explore the underlying mechanisms. The results showed that exposure to high relative humidity or to 0.5 mg/m³ formaldehyde alone had a slight, but not significant, affect on allergic asthma. However, the pathological response and airway hyperresponsiveness (AHR) were greatly aggravated by simultaneous exposure to 0.5 mg/m³ formaldehyde and 90% relative humidity. Blocking TRPV4or p38 MAPK using HC-067047 and SB203580 respectively, effectively alleviated the exacerbation of allergic asthma induced by this simultaneous exposure to formaldehyde and high relative humidity. The results show that when formaldehyde and high relative humidity are present this can enhance the activation of the TRPV4 ion channel in the lung leading to the aggravation of the p38 MAPK activation, resulting in the exacerbation of inflammation and hypersecretion of mucus in the airways.

Viruses and non-allergen environmental triggers in asthma

Asthma is a complex inflammatory disease with many triggers. The best understood asthma inflammatory pathways involve signals characterized by peripheral eosinophilia and elevated immunoglobulin E levels (called T2-high or allergic asthma), though other asthma phenotypes exist (eg, T2-low or non-allergic asthma, eosinophilic or neutrophilic-predominant). Common triggers that lead to poor asthma control and exacerbations include respiratory viruses, aeroallergens, house dust, molds, and other organic and inorganic substances. Increasingly recognized non-allergen triggers include tobacco smoke, small particulate matter (eg, PM2.5), and volatile organic compounds. The interaction between respiratory viruses and non-allergen asthma triggers is not well understood, though it is likely a connection exists which may lead to asthma development and/or exacerbations. In this paper we describe common respiratory viruses and non-allergen triggers associated with asthma. In addition, we aim to show the possible interactions, and potential synergy, between viruses and non-allergen triggers. Finally, we introduce a new clinical approach that collects exhaled breath condensates to identify metabolomics associated with viruses and non-allergen triggers that may promote the early management of asthma symptoms.

Protective role of (Bronco-T) against formaldehyde induced antioxidant, oxidative and histopathological changes in lung of male Wistar rats

The present study was sought to evaluate the oxidative, antioxidant status and histopathological changes by the acute chronic exposure of formaldehyde. Bronco-T a poly-herbal formulation treatment, changes the oxidative, antioxidant status and histopathology of rat lungs with antioxidant and regenerative property. In this experiment thirty adult male albino Wister rats were used for the study and subdivided in to five groups consist of 6 rats for each group. Group-I served as control and the other 4 groups such as II, III, IV and V are considered as experimental. The control and treatment rats are maintained for 21 days of experimental period. Experimental rats are exposed to 40 percent formaldehyde for 1 h treated with Bronco-T and salbutamol. In the present investigation, the formaldehyde exposed rats a series of free radical chain reactions were grimly provoked, the evaluation of antioxidant enzymes (SOD, CAT), other enzymes oxidative enzymes (G-6-PDH, SDH) and (ALT, ALAT and LDH) were measured. A clear assertive imbalance between oxidation and anti-oxidation status was critically observed, and oxidative stress was clearly exacerbated in lung tissue leading to altrations in architecture of lung histopathology. Oral gavage Bronco-T exhibits a beneficial action by bringing normal architecture in lung tissue of formaldehyde inhaled rats with antioxidant properties. Bronco-T treatment may be a suitable remedy for formalin occupational diseases.

Reactive paper spray mass spectrometry for rapid analysis of formaldehyde in facial masks

RATIONALE

A reactive paper spray mass spectrometric approach for rapid analysis of formaldehyde (FA) in cosmetics was developed based on an on-line derivatization reaction between formaldehyde and dansyl hydrazine (DH).

METHODS

The whole experimental procedure consists of three simple steps: (1) load the sample (2 μL) onto the paper; (2) add the spray solvent (10 μL DH); (3) apply a high voltage (+4.5 kV) to the sample. We used an internal standard (dansyl amide) to create the analytical calibration curve. The established approach has been successfully applied in the quantitation of FA in facial masks.

RESULTS

Our approach shows good linearity for the FA concentrations between 3 and 300 μg L^-1 , and the limit of detection is at 0.8 μg L^-1 . Five brands of facial masks were analyzed by this approach without any sample pretreatment, and the FA contents varied from 0.05 to 2.6 mg L^-1 with favorable recoveries achieved between 93.2% and 111.3%.

CONCLUSIONS

This established approach presents a solution to rapid quantitation at extremely low cost of consumables and has potential as a simple, sensitive and robust strategy for the direct analysis of FA in cosmetics, food, environmental, and biological samples.

A two-photon fluorescent probe for basal formaldehyde imaging in zebrafish and visualization of mitochondrial damage induced by FA stress

A two-photon fluorescence probe Mito-FA-FP can monitor mitochondrial morphology change and image endogenous FA in vivo.

Measured moisture in buildings and adverse health effects: A review

It has not yet been possible to quantify dose-related health risks attributable to indoor dampness or mold (D/M), to support setting specific health-related limits for D/M. An overlooked target for assessing D/M is moisture in building materials, the critical factor allowing microbial growth. A search for studies of quantified building moisture and occupant health effects identified 3 eligible studies. Two studies assessed associations between measured wall moisture content and respiratory health in the UK. Both reported dose-related increases in asthma exacerbation with higher measured moisture, with 1 study reporting an adjusted odds ratio of 7.0 for night-time asthma symptoms with higher bedroom moisture. The third study assessed relationships between infrared camera-determined wall moisture and atopic dermatitis in South Korea, reporting an adjusted odds ratio of 14.5 for water-damaged homes and moderate or severe atopic dermatitis. Measuring building moisture has, despite extremely limited available findings, potential promise for detecting unhealthy D/M in homes and merits more research attention. Further research to validate these findings should include measured "water activity," which directly assesses moisture availability for microbial growth. Ultimately, evidence-based, health-related thresholds for building moisture, across specific materials and measurement devices, could better guide assessment and remediation of D/M in buildings.

Differential effects of formaldehyde exposure on airway inflammation and bronchial hyperresponsiveness in BALB/c and C57BL/6 mice

Epidemiological evidence suggests that formaldehyde (FA) exposure may influence the prevalence and severity of allergic asthma. However, the role of genetic background in FA-induced asthma-like responses is poorly understood. In the present study, we investigated the nature and severity of asthma-like responses triggered by exposure to different doses of FA together with or without ovalbumin (OVA) in two genetically different mouse strains—BALB/c and C57BL/6. Both mouse strains were divided into two main groups: the non-sensitized group and the OVA-sensitized group. All the groups were exposed to 0, 0.5 or 3.0 mg/m³ FA for 6 h/day over 25 consecutive days. At 24 h after the final FA exposure, the pulmonary parameters were evaluated. We found that FA exposure induced Th2-type allergic responses in non-sensitized BALB/c and C57BL/6 mice. In addition, FA-induced allergic responses were significantly more prominent in BALB/c mice than in C57BL/6 mice. In sensitized BALB/c mice, however, FA exposure suppressed the development of OVA-induced allergic responses. Exposure to 3.0 mg/m³ FA in sensitized C57BL/6 mice also led to suppressed allergic responses, whereas exposure to 0.5 mg/m³ FA resulted in exacerbated allergic responses to OVA. Our findings suggest that FA exposure can induce differential airway inflammation and bronchial hyperresponsiveness in BALB/c and C57BL/6 mice.

Potential hazards of air pollutant emissions from unconventional oil and natural gas operations on the respiratory health of children and infants

Research on air pollutant emissions associated with unconventional oil and gas (UOG) development has grown significantly in recent years. Empirical investigations have focused on the identification and measurement of oil and gas air pollutants [e.g. volatile organic compounds (VOCs), particulate matter (PM), methane] and the influence of UOG on local and regional ambient air quality (e.g. tropospheric ozone). While more studies to better characterize spatial and temporal trends in exposure among children and newborns near UOG sites are needed, existing research suggests that exposure to air pollutants emitted during lifecycle operations can potentially lead to adverse respiratory outcomes in this population. Children are known to be at a greater risk from exposure to air pollutants, which can impair lung function and neurodevelopment, or exacerbate existing conditions, such as asthma, because the respiratory system is particularly vulnerable during development in-utero, the postnatal period, and early childhood. In this article, we review the literature relevant to respiratory risks of UOG on infants and children. Existing epidemiology studies document the impact of air pollutant exposure on children in other contexts and suggest impacts near UOG. Research is sparse on long-term health risks associated with frequent acute exposures - especially in children - hence our interpretation of these findings may be conservative. Many data gaps remain, but existing data support precautionary measures to protect the health of infants and children.

Oxidative effects on lung inflammatory response in rats exposed to different concentrations of formaldehyde

The formaldehyde (FA) is a crosslinking agent that reacts with cellular macromolecules such as proteins, nucleic acids and molecules with low molecular weight such as amino acids, and it has been linked to inflammatory processes and oxidative stress. This study aimed to analyze the oxidative effects on pulmonary inflammatory response in Fischer rats exposed to different concentrations of FA. Twenty-eight Fischer rats were divided into 4 groups (N = 7). The control group (CG) was exposed to ambient air and three groups were exposed to different concentrations of FA: 1% (FA1%), 5% (FA5%) and 10% (FA10%). In the Bronchoalveolar Lavage Fluid (BALF), the exposure to a concentration of 10% promoted the increase of inflammatory cells compared to CG. There was also an increase of macrophages and lymphocytes in FA10% and lymphocytes in FA5% compared to CG. The activity of NADPH oxidase in the blood had been higher in FA5% and FA10% compared to CG. The activity of superoxide dismutase enzyme (SOD) had an increase in FA5% and the activity of the catalase enzyme (CAT) showed an increase in FA1% compared to CG. As for the glutathione system, there was an increase in total glutathione (tGSH), reduced glutathione (GSH) and oxidized glutathione (GSSG) in FA5% compared to CG. The reduced/oxidized glutathione ratio (GSH/GSSG) had a decrease in FA5% compared to CG. There was an increase in lipid peroxidation compared to all groups and the protein carbonyl formation in FA10% compared to CG. We also observed an increase in CCL2 and CCL5 chemokines in the treatment groups compared to CG and in serum there was an increase in CCL2, CCL3 and CCL5 compared to CG. Our results point out to the potential of formaldehyde in promoting airway injury by increasing the inflammatory process as well as by the redox imbalance.

Obstructive Sleep Apnoea Modulates Airway Inflammation and Remodelling in Severe Asthma

Background

Obstructive sleep apnoea (OSA) is frequently observed in severe asthma but the causal link between the 2 diseases remains hypothetical. The role of OSA-related systemic and airway neutrophilic inflammation in asthma bronchial inflammation or remodelling has been rarely investigated. The aim of this study was to compare hallmarks of inflammation in induced sputum and features of airway remodelling in bronchial biopsies from adult patients with severe asthma with and without OSA.

Materials and Methods

An overnight polygraphy was performed in 55 patients referred for difficult-to-treat asthma, who complained of nocturnal respiratory symptoms, poor sleep quality or fatigue. We compared sputum analysis, reticular basement membrane (RBM) thickness, smooth muscle area, vascular density and inflammatory cell infiltration in bronchial biopsies.

Results

In total, 27/55 patients (49%) had OSA diagnosed by overnight polygraphy. Despite a moderate increase in apnoea-hypopnoea index (AHI; 14.2±1.6 event/h [5–35]), the proportion of sputum neutrophils was higher and that of macrophages lower in OSA than non-OSA patients, with higher levels of interleukin 8 and matrix metalloproteinase 9. The RBM was significantly thinner in OSA than non-OSA patients (5.8±0.4 vs. 7.8±0.4 μm, p<0.05). RBM thickness and OSA severity assessed by the AHI were negatively correlated (rho = -0.65, p<0.05). OSA and non-OSA patients did not differ in age, sex, BMI, lung function, asthma control findings or treatment.

Conclusion

Mild OSA in patients with severe asthma is associated with increased proportion of neutrophils in sputum and changes in airway remodelling.

Short-term exposure to formaldehyde promotes oxidative damage and inflammation in the trachea and diaphragm muscle of adult rats

Formaldehyde (FA) is an environmental pollutant widely used in industry. Exposure to FA causes irritation of the respiratory mucosa and is associated with inflammation and oxidative stress in the airways. This study aimed at investigating the oxidative effects on the inflammatory response in the trachea and the diaphragm muscle (DM) of rats exposed to different concentrations of formaldehyde. Twenty-eight Fischer male rats were divided into four groups: control group (CG) exposed to the ambient air; and three groups exposed to the following formaldehyde concentrations of 1% (FA1), 5% (FA5) and 10% (FA10), respectively. The exposure occurred for twenty minutes, three times a day for five days. Oxidative stress analyses were performed by carbonyl protein, lipid peroxidation and catalase activity. The assessment of inflammatory cell influx in both organs and the mucus production in the trachea was carried out. There was an increase of lipid peroxidation in the trachea and the DM of FA1 and FA5 groups compared to the CG and FA10. The oxidation of DM proteins increased in FA10 group compared to CG, FA1 and FA5. The catalase enzyme activity in the DM was reduced in FA1, FA5 and FA10 compared to the CG. Meanwhile, there was a reduction in the enzymatic activity of FA10 compared to the CG in the trachea. The morphometric analysis in the DM demonstrated an influx of inflammatory cells in FA10 compared to the CG. In FA10 group, the tracheal epithelium showed metaplasia and ulceration. In addition, the tracheal epithelium showed more mucus deposits in FA5 compared to CG, FA1 and FA10. The results demonstrated that the exposure to formaldehyde at different concentrations in a short period of time promotes oxidative damage and inflammation in the DM and the trachea and causes metaplasia, ulceration and increased mucus at the latter.

In situ facile-forming PEG cross-linked albumin hydrogels loaded with an apoptotic TRAIL protein

The key to making a practicable hydrogel for pharmaceutical or medical purposes is to endow it with relevant properties, i.e., facile fabrication, gelation time-controllability, and in situ injectability given a firm basis for safety/biocompatibility. Here, the authors describe an in situ gelling, injectable, albumin-cross-linked polyethylene glycol (PEG) hydrogel that was produced using a thiol-maleimide reaction. This hydrogel consists of two biocompatible components, namely, thiolated human serum albumin and 4-arm PEG20k-maleimide, and can be easily fabricated and gelled in situ within 60s by simply mixing its two components. In addition, the gelation time of this system is controllable in the range 15s to 5min. This hydrogel hardly interacted with an apoptotic TRAIL protein, ensuring suitable release profiles that maximize therapeutic efficacy. Specifically, tumors (volume: 278.8mm(3)) in Mia Paca-2 cell-xenografted BALB/c nu/nu mice treated with the TRAIL-loaded HSA-PEG hydrogel were markedly smaller than mice treated with the hydrogel prepared via an amine-N-hydroxysuccinimide reaction or non-treated mice (1275.5mm(3) and 1816.5mm(3), respectively). We believe that this hydrogel would be a new prototype of locally injectable sustained-release type anti-cancer agents, and furthermore offers practical convenience for a doctor and universal applicability for a variety of therapeutic proteins.

Indoor environmental exposures and exacerbation of asthma: an update to the 2000 review by the Institute of Medicine

BACKGROUND

Previous research has found relationships between specific indoor environmental exposures and exacerbation of asthma.

OBJECTIVES

In this review we provide an updated summary of knowledge from the scientific literature on indoor exposures and exacerbation of asthma.

METHODS

Peer-reviewed articles published from 2000 to 2013 on indoor exposures and exacerbation of asthma were identified through PubMed, from reference lists, and from authors' files. Articles that focused on modifiable indoor exposures in relation to frequency or severity of exacerbation of asthma were selected for review. Research findings were reviewed and summarized with consideration of the strength of the evidence.

RESULTS

Sixty-nine eligible articles were included. Major changed conclusions include a causal relationship with exacerbation for indoor dampness or dampness-related agents (in children); associations with exacerbation for dampness or dampness-related agents (in adults), endotoxin, and environmental tobacco smoke (in preschool children); and limited or suggestive evidence for association with exacerbation for indoor culturable Penicillium or total fungi, nitrogen dioxide, rodents (nonoccupational), feather/down pillows (protective relative to synthetic bedding), and (regardless of specific sensitization) dust mite, cockroach, dog, and dampness-related agents.

DISCUSSION

This review, incorporating evidence reported since 2000, increases the strength of evidence linking many indoor factors to the exacerbation of asthma. Conclusions should be considered provisional until all available evidence is examined more thoroughly.

CONCLUSION

Multiple indoor exposures, especially dampness-related agents, merit increased attention to prevent exacerbation of asthma, possibly even in nonsensitized individuals. Additional research to establish causality and evaluate interventions is needed for these and other indoor exposures.

Aberrant production of Th1/Th2/Th17-related cytokines in serum of C57BL/6 mice after short-term formaldehyde exposure

Previous studies have shown that formaldehyde (FA) could cause immunotoxicity by changing the number of T lymphocytes and that cytokines play a pivotal role in the regulation of T lymphocytes. However, the previously used cytokine detection methods are difficult to use in the measurement of several cytokines in a small amount of sample for one test. Therefore, the cytometric bead array (CBA) technique was used. CBA showed better analytical efficiency and sensitivity than the previous methods. C57BL/6 mice were exposed to the control (normal saline), low FA concentration (0.5 mg/kg), and high FA concentration (2 mg/kg) for 1 week or 1 month. The contents of cytokines, including Th1-related cytokines (IL-2, IFN-γ, and tumor necrosis factor), Th2-related cytokines (IL-4, IL-6, and IL-10), and Th17-related cytokines (IL-17A), were measured by using the BD FACS Canto II Flow Cytometer and analyzed by FCAP ArrayTM Software. Th1/Th2/Th17-related cytokines showed a slightly decreasing trend after low FA exposure. Conversely, a significantly increasing trend was found after high FA exposure. Th1/Th2/Th17-related cytokines all serve important functions in the immune reactions in mice after FA exposure.

Repeated nitrogen dioxide exposures and eosinophilic airway inflammation in asthmatics: a randomized crossover study

BACKGROUND

Nitrogen dioxide (NO2), a ubiquitous atmospheric pollutant, may enhance the asthmatic response to allergens through eosinophilic activation in the airways. However, the effect of NO2 on inflammation without allergen exposure is poorly studied.

OBJECTIVES

We investigated whether repeated peaks of NO2, at various realistic concentrations, induce changes in airway inflammation in asthmatics.

METHODS

Nineteen nonsmokers with asthma were exposed at rest in a double-blind, crossover study, in randomized order, to 200 ppb NO2, 600 ppb NO2, or clean air once for 30 min on day 1 and twice for 30 min on day 2. The three series of exposures were separated by 2 weeks. The inflammatory response in sputum was measured 6 hr (day 1), 32 hr (day 2), and 48 hr (day 3) after the first exposure, and compared with baseline values measured twice 10-30 days before the first exposure.

RESULTS

Compared with baseline measurements, the percentage of eosinophils in sputum increased by 57% after exposure to 600 ppb NO2 (p = 0.003) but did not change significantly after exposure to 200 ppb. The slope of the association between the percentage of eosinophils and NO2 exposure level was significant (p = 0.04). Eosinophil cationic protein in sputum was highly correlated with eosinophil count and increased significantly after exposure to 600 ppb NO2 (p = 0.001). Lung function, which was assessed daily, was not affected by NO2 exposure.

CONCLUSIONS

We observed that repeated peak exposures of NO2 performed without allergen exposure were associated with airway eosinophilic inflammation in asthmatics in a dose-related manner.

Exposure to low doses of formaldehyde during pregnancy suppresses the development of allergic lung inflammation in offspring

Formaldehyde (FA) is an environmental and occupational pollutant, and its toxic effects on the immune system have been shown. Nevertheless, no data are available regarding the programming mechanisms after FA exposure and its repercussions for the immune systems of offspring. In this study, our objective was to investigate the effects of low-dose exposure of FA on pregnant rats and its repercussion for the development of allergic lung inflammation in offspring. Pregnant Wistar rats were assigned in 3 groups: P (rats exposed to FA (0.75 ppm, 1 h/day, 5 days/week, for 21 days)), C (rats exposed to vehicle of FA (distillated water)) and B (rats non-manipulated). After 30 days of age, the offspring was sensitised with ovalbumin (OVA)-alum and challenged with aerosolized OVA (1%, 15 min, 3 days). After 24 h the OVA challenge the parameters were evaluated. Our data showed that low-dose exposure to FA during pregnancy induced low birth weight and suppressed the development of allergic lung inflammation and tracheal hyperresponsiveness in offspring by mechanisms mediated by reduced anaphylactic antibodies synthesis, IL-6 and TNF-alpha secretion. Elevated levels of IL-10 were found. Any systemic alteration was detected in the exposed pregnant rats, although oxidative stress in the uterine environment was evident at the moment of the delivery based on elevated COX-1 expression and reduced cNOS and SOD-2 in the uterus. Therefore, we show the putative programming mechanisms induced by FA on the immune system for the first time and the mechanisms involved may be related to oxidative stress in the foetal microenvironment.

Identifying asthma triggers

Asthma has many triggers including rhinosinusitis; allergy; irritants; medications (aspirin in aspirin-exacerbated respiratory disease); and obesity. Paradoxic vocal fold dysfunction mimics asthma and may be present along with asthma. This article reviews each of these triggers, outlining methods of recognizing the trigger and then its management. In many patients more than one trigger may be present. Full appreciation of the complexity of these relationships and targeted therapy to the trigger is needed to best care for the patient with asthma.

Formaldehyde inhalation reduces respiratory mechanics in a rat model with allergic lung inflammation by altering the nitric oxide/cyclooxygenase-derived products relationship

Bronchial hyperresponsiveness is a hallmark of asthma and many factors modulate bronchoconstriction episodes. A potential correlation of formaldehyde (FA) inhalation and asthma has been observed; however, the exact role of FA remains controversial. We investigated the effects of FA inhalation on Ovalbumin (OVA) sensitisation using a parameter of respiratory mechanics. The involvement of nitric oxide (NO) and cyclooxygenase-derived products were also evaluated. The rats were submitted, or not, to FA inhalation (1%, 90 min/day, 3 days) and were OVA-sensitised and challenged 14 days later. Our data showed that previous FA exposure in allergic rats reduced bronchial responsiveness, respiratory resistance (Rrs) and elastance (Ers) to methacholine. FA exposure in allergic rats also increased the iNOS gene expression and reduced COX-1. L-NAME treatment exacerbated the bronchial hyporesponsiveness and did not modify the Ers and Rrs, while Indomethacin partially reversed all of the parameters studied. The L-NAME and Indomethacin treatments reduced leukotriene B₄ levels while they increased thromboxane B₂ and prostaglandin E₂. In conclusion, FA exposure prior to OVA sensitisation reduces the respiratory mechanics and the interaction of NO and PGE₂ may be representing a compensatory mechanism in order to protect the lung from bronchoconstriction effects.

Role of transient receptor potential ion channels and evoked levels of neuropeptides in a formaldehyde-induced model of asthma in BALB/c mice

OBJECTIVE

Asthma is a complex pulmonary inflammatory disease characterized by the hyper-responsiveness, remodeling and inflammation of airways. Formaldehyde is a common indoor air pollutant that can cause asthma in people experiencing long-term exposure. The irritant effect and adjuvant effect are the two possible pathways of formaldehyde promoted asthma.

METHODOLOGY/PRINCIPAL FINDINGS

To explore the neural mechanisms and adjuvant effect of formaldehyde, 48 Balb/c mice in six experimental groups were exposed to (a) vehicle control; (b) ovalbumin; (c) formaldehyde (3.0 mg/m(3)); (d) ovalbumin+formaldehyde (3.0 mg/m(3)); (e) ovalbumin+formaldehyde (3.0 mg/m(3))+HC-030031 (transient receptor potential ankyrin 1 antagonist); (f) ovalbumin+formaldehyde (3.0 mg/m(3))+ capsazepine (transient receptor potential vanilloid 1 antagonist). Experiments were conducted after 4 weeks of combined exposure and 1-week challenge with aerosolized ovalbumin. Airway hyper-responsiveness, pulmonary tissue damage, eosinophil infiltration, and increased levels of interleukin-4, interleukin-6, interleukin-1β, immunoglobulin E, substance P and calcitonin gene-related peptide in lung tissues were found in the ovalbumin+formaldehyde (3.0 mg/m(3)) group compared with the values seen in ovalbumin -only immunized mice. Except for interleukin-1β levels, other changes in the levels of biomarker could be inhibited by HC-030031 and capsazepine.

CONCLUSIONS/SIGNIFICANCE

Formaldehyde might be a key risk factor for the rise in asthma cases. Transient receptor potential ion channels and neuropeptides have important roles in formaldehyde promoted-asthma.

Identifying an indoor air exposure limit for formaldehyde considering both irritation and cancer hazards

Formaldehyde is a well-studied chemical and effects from inhalation exposures have been extensively characterized in numerous controlled studies with human volunteers, including asthmatics and other sensitive individuals, which provide a rich database on exposure concentrations that can reliably produce the symptoms of sensory irritation. Although individuals can differ in their sensitivity to odor and eye irritation, the majority of authoritative reviews of the formaldehyde literature have concluded that an air concentration of 0.3 ppm will provide protection from eye irritation for virtually everyone. A weight of evidence-based formaldehyde exposure limit of 0.1 ppm (100 ppb) is recommended as an indoor air level for all individuals for odor detection and sensory irritation. It has recently been suggested by the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), and the US Environmental Protection Agency (US EPA) that formaldehyde is causally associated with nasopharyngeal cancer (NPC) and leukemia. This has led US EPA to conclude that irritation is not the most sensitive toxic endpoint and that carcinogenicity should dictate how to establish exposure limits for formaldehyde. In this review, a number of lines of reasoning and substantial scientific evidence are described and discussed, which leads to a conclusion that neither point of contact nor systemic effects of any type, including NPC or leukemia, are causally associated with exposure to formaldehyde. This conclusion supports the view that the equivocal epidemiology studies that suggest otherwise are almost certainly flawed by identified or yet to be unidentified confounding variables. Thus, this assessment concludes that a formaldehyde indoor air limit of 0.1 ppm should protect even particularly susceptible individuals from both irritation effects and any potential cancer hazard.

Do indoor environments influence asthma and asthma-related symptoms among adults in homes?: a review of the literature

This review summarizes the results of epidemiological studies focusing on the detrimental effects of home environmental factors on asthma morbidity in adults. We reviewed the literature on indoor air quality (IAQ), physical and sociodemographic factors, and asthma morbidity in homes, and identified commonly reported asthma, allergic, and respiratory symptoms involving the home environment. Reported IAQ and asthma morbidity data strongly indicated positive associations between indoor air pollution and adverse health effects in most studies. Indoor factors most consistently associated with asthma and asthma-related symptoms in adults included fuel combustion, mold growth, and environmental tobacco smoke. Environmental exposure may increase an adult's risk of developing asthma and also may increase the risk of asthma exacerbations. Evaluation of present IAQ levels, exposure characteristics, and the role of exposure to these factors in relation to asthma morbidity is important for improving our understanding, identifying the burden, and for developing and implementing interventions aimed at reducing asthma morbidity.

Quantitative assessments of indoor air pollution and respiratory health in a population-based sample of French dwellings

BACKGROUND

Various volatile organic compounds (VOCs) have been related to respiratory health effects, but have generally been assessed individually without taking into account the fact that such pollutants are highly correlated to one other.

AIMS

We investigated the effects of exposure to various VOC, and considered their combined effect on adult asthma and rhinitis.

METHOD

A national cross-sectional representative survey conducted by the Indoor Air Quality Observatory objectively assessed 20 VOCs in 490 main dwellings in France. A standardized questionnaire determined the prevalence of asthma and rhinitis among 1012 inhabitants of the dwellings (≥ 15 years). Marginal models for binary outcome were used to relate VOCs exposure to asthma and rhinitis, controlling for potential confounders. A global score representing the number of VOCs in each dwelling with an elevated concentration (using the 3(rd) quartile value of the distribution as a threshold value) was then derived as a measure of the combined effect of VOCs. Specific scores were built using a similar approach, grouping VOCs by family.

RESULTS

Asthma (8.6%) was significantly associated with N-undecane and 1,2,4-trimethylbenzene and rhinitis (38.3%) with ethylbenzene, trichloroethylene, m/p- and o-xylene. The global VOC score was associated with a significant risk of asthma and rhinitis (odds ratio (OR) of 1.40 and 1.22, respectively, for 5 additional VOCs with high exposure level). Both specific scores for aromatic hydrocarbons and aliphatic hydrocarbons were associated with a significantly risk of asthma (OR=1.12; 95% confidence interval (CI): 1.01-1.24 and OR=1.41; 95% CI=1.03-1.93, respectively). The specific VOC score for halogenated hydrocarbons was associated with a significant risk of rhinitis (OR=1.28; 95% CI: 1.07-1.54).

CONCLUSION

We have shown that high concentrations of VOCs in homes were associated with an increasing prevalence of asthma and rhinitis in adults.

Early changes to oxidative stress levels following exposure to formaldehyde in ICR mice

Formaldehyde (FA) is a commonly used chemical in everyday life and can react with many molecules in the human body. Although toxicity has been reported, exposure to FA has also been shown to have beneficial effects or no effect at all. In the present study, we examined the effect of FA inhalation on oxidative stress and inflammation in mice. Male adult ICR mice were exposed FA in gaseous form (0.1 ppm), and blood, urine, brain, lung and liver were obtained for 24 hr. Levels of 8-hydroxy-2'-deoxyguanosine (8OHdG) and NO(3)(-) were then determined by HPLC. A second group of mice were injected with 5 mg/kg lipopolysaccharide (LPS) after 24 hr of FA (3 ppm) inhalation and blood and organs were assayed for NO(3)(-) level and SOD activity. After exposure to a low dose of FA (0.1 ppm), the 8OHdG/dG ratio significantly increased in plasma. However, the ratio in urine and organs significantly decreased during 24 hr of FA exposure. The NO(3)(-) levels mirrored the 8OHdG/dG ratio. After 24 hr exposure to a high dose of FA (3 ppm), NO(3)(-) levels in plasma and liver were significantly lower than in control mice exposed to air only. The SOD activity of blood and urine were conversely increased in FA exposed animals. In the present study, we suggest that inhalation of FA at low doses influences the oxidative stress response in a tissue-specific manner. The FA may partially alleviate in some tissues like preconditioning in oxidative stress.

Formaldehyde interferes with airway epithelium integrity and functions in a dose- and time-dependent manner

Formaldehyde (HCHO) is a common indoor air pollutant. To assess its potential role and mechanism of action in asthma, we exposed the bronchial epithelial cell lines Calu-3 and 16HBE to HCHO (70-7000 μM) according to two exposure schedules (30 min and 24 h), before measuring cell viability, necrosis and apoptosis, reactive oxygen species production, cytokine release, as well as trans-epithelial electrical resistance (TEER) of cell monolayers. Whereas exposure to HCHO for 30 min had a limited effect on cell viability, exposure for 24h to 1400-7000 μM HCHO induced a pronounced dose-dependent cell death. The important decrease in cell viability observed after 24h exposure to the highest concentrations of HCHO (1400-7000 μM) was accompanied by important LDH release and ROS production, whereas a 4h exposure to lower HCHO concentrations (350 μM) induced cell apoptosis. Also, exposure to HCHO for 30 min dose-dependently inhibited basal and lipopolysaccharide-induced interleukin-6 (IL-6) and IL-8 production by bronchial epithelial cells. As well, HCHO triggered a dose- and time-dependent decrease in TEER of Calu-3 cell monolayers. The present work demonstrates that HCHO interferes with airway epithelium integrity and functions, and may thus modulate the onset and the severity of asthma. However, importantly, conditions of exposure to HCHO, e.g. level and duration, are determinant in the nature of the effects triggered by the pollutant.

Non-cancer effects of formaldehyde and relevance for setting an indoor air guideline

There is considerable recent focus and concern about formaldehyde (FA). We have reviewed the literature on FA with focus on chemosensory perception in the airways and lung effects in indoor environments. Concentrations of FA, both personal and stationary, are on average in the order of 0.05 mg/m(3) or less in Europe and North America with the exception of new housing or buildings with extensive wooden surfaces, where the concentration may exceed 0.1 mg/m(3). With the eye the most sensitive organ, subjective irritation is reported at 0.3-0.5 mg/m(3), which is somewhat higher than reported odour thresholds. Objective effects in the eyes and airways occur around 0.6-1 mg/m(3). Dose-response relationships between FA and lung function effects have not been found in controlled human exposure studies below 1 mg/m(3), and epidemiological associations between FA concentrations and exacerbation of asthma in children and adults are encumbered by complex exposures. Neither experimental nor epidemiological studies point to major differences in susceptibility to FA among children, elderly, and asthmatics. People with personal trait of negative affectivity may report more symptoms. An air quality guideline of 0.1 mg/m(3) (0.08 ppm) is considered protective against both acute and chronic sensory irritation in the airways in the general population assuming a log normal distribution of nasal sensory irritation.

Production and in vitro evaluation of soy protein-based biofilms as a support for human keratinocyte and fibroblast culture

This study presents results on soy protein isolate (SPI) biofilm production and the corresponding effect on the stability and toxicity of the derived films. SPI biofilms were prepared from SPI chemically treated with formaldehyde at various concentrations (0%, 1%, 2%, and 3%) as cross-linking agents. In vitro SPI biofilm degradation was evaluated as a function of water absorption leading to weight and size modifications. SPI biofilm toxicity was determined as a function of human keratinocyte and fibroblast adhesion, viability, and proliferation. Cytokine gene expression supported this using reverse transcriptase polymerase chain reaction techniques. Our results confirm that SPI can be used to produce biofilms. The resulting SPI biofilms without formaldehyde swell significantly, which leads to their physical instability. Formaldehyde treatment enhanced the mechanical properties of these biofilms by covalently cross-linking polypeptide chains. The decreased water absorption was dependent on the amount of formaldehyde present. SPI biofilms with 2% and 3% formaldehyde were highly stable and easier to manipulate than those with 0% and 1% formaldehyde. Tissue culture analyses revealed that the SPI biofilms without formaldehyde were non-toxic to human cells (keratinocytes and fibroblasts). The presence of formaldehyde in biofilms did not have any effects on cell viability, adhesion, or proliferation. This was supported by the high level of messenger RNA expression of interleukin-1 beta (IL-1beta) and tumor necrosis factor alpha by the keratinocytes and of IL-6 and IL-8 by the fibroblasts. Overall, we produced a stable, non-toxic soy protein support, which may be of potential interest in medical applications such as cell culture matrices and damaged tissue replacement.

The ontogeny, distribution, and regulation of alcohol dehydrogenase 3: implications for pulmonary physiology

Class III alcohol dehydrogenase (ADH3), also termed formaldehyde dehydrogenase or S-nitrosoglutathione reductase, plays a critical role in the enzymatic oxidation of formaldehyde and reduction of nitrosothiols that regulate bronchial tone. Considering reported associations between formaldehyde vapor exposure and childhood asthma risk, and thus potential involvement of ADH3, we reviewed the ontogeny, distribution, and regulation of mammalian ADH3. Recent studies indicate that multiple biological and chemical stimuli influence expression and activity of ADH3, including the feedback regulation of nitrosothiol metabolism. The levels of ADH3 correlate with, and potentially influence, bronchial tone; however, data gaps remain with respect to the expression of ADH3 during postnatal and early childhood development. Consideration of ADH3 function relative to the respiratory effects of formaldehyde, as well as to other chemical and biological exposures that might act in an additive or synergistic manner with formaldehyde, might be critical to gain better insight into the association between formaldehyde exposure and childhood asthma.

Reduced allergic lung inflammation in rats following formaldehyde exposure: long-term effects on multiple effector systems

Clinical and experimental evidences show that formaldehyde (FA) exposure has an irritant effect on the upper airways. As being an indoor and outdoor pollutant, FA is known to be a causal factor of occupational asthma. This study aimed to investigate the repercussion of FA exposure on the course of a lung allergic process triggered by an antigen unrelated to FA. For this purpose, male Wistar rats were subjected to FA inhalation for 3 consecutive days (1%, 90-min daily), subsequently sensitized with ovalbumin (OVA)-alum via the intraperitoneal route, and 2 weeks later challenged with aerosolized OVA. The OVA challenge in rats after FA inhalation (FA/OVA group) evoked a low-intensity lung inflammation as indicated by the reduced enumerated number of inflammatory cells in bronchoalveolar lavage as compared to FA-untreated allergic rats (OVA/OVA group). Treatment with FA also reduced the number of bone marrow cells and blood leukocytes in sensitized animals challenged with OVA, which suggests that the effects of FA had not been only localized to the airways. As indicated by passive cutaneous anaphylactic reaction, FA treatment did not impair the anti-OVA IgE synthesis, but reduced the magnitude of OVA challenge-induced mast cell degranulation. Moreover, FA treatment was associated to a diminished lung expression of PECAM-1 (platelet-endothelial cell adhesion molecule 1) in lung endothelial cells after OVA challenge and an exacerbated release of nitrites by BAL-cultured cells. Keeping in mind that rats subjected solely to either FA or OVA challenge were able to significantly increase the cell influx into lung, our study shows that FA inhalation triggers long-lasting effects that affect multiple mediator systems associated to OVA-induced allergic lung such as the reduction of mast cells activation, PECAM-1 expression and exacerbation of NO generation, thereby contributing to the decrease of cell recruitment after the OVA challenge. In conclusion, repeated expositions to air-borne FA may impair the lung cell recruitment after an allergic stimulus, thereby leading to a non-responsive condition against inflammatory stimuli likely those where mast cells are involved.

Mechanistic and dose considerations for supporting adverse pulmonary physiology in response to formaldehyde

Induction of airway hyperresponsiveness and asthma from formaldehyde inhalation exposure remains a debated and controversial issue. Yet, recent evidences on pulmonary biology and the pharmacokinetics and toxicity of formaldehyde lend support for such adverse effects. Specifically, altered thiol biology from accelerated enzymatic reduction of the endogenous bronchodilator S-nitrosoglutathione and pulmonary inflammation from involvement of Th2-mediated immune responses might serve as key events and cooperate in airway pathophysiology. Understanding what role these mechanisms play in various species and lifestages (e.g., child vs. adult) could be crucial for making more meaningful inter- and intra-species dosimetric extrapolations in human health risk assessment.

Mechanistic considerations for formaldehyde-induced bronchoconstriction involving S-nitrosoglutathione reductase

Inhalation of formaldehyde vapor has long been suspected of producing airway pathophysiology such as asthma and hyperresponsivity, presumably via irritant mechanisms. Recent studies on asthma and airway biology implicate changes in nitric oxide (NO) disposition in the adverse effects of formaldehyde, principally because enzymatic reduction of the endogenous bronchodilator S-nitrosoglutathione (GSNO) is dependent upon GSNO reductase (formally designated as alcohol dehydrogenase-3, ADH3), which also serves as the primary enzyme for cellular detoxification of formaldehyde. Considering recent evidence that regulation of bronchodilators like GSNO might play a more important role in asthma than inflammation per se, formaldehyde also needs to be considered as influencing ADH3-mediated GSNO catabolism. This is due to changes in ADH3 cofactors and thiol redox state among several potential mechanisms. Data suggest that deregulation of GSNO turnover provides a plausible, enzymatically based mechanism by which formaldehyde might exacerbate asthma and induce bronchoconstriction.

Formaldehyde and chemosensory irritation in humans: a controlled human exposure study

OBJECTIVES

The objective of this study was to examine the possible occurrence of sensory irritation and subjective symptoms in human volunteers exposed to formaldehyde concentrations relevant to the workplace. The set up of the study included formaldehyde exposures with and without peaks, the presence and absence of a masking agent, and evaluation of the influence of personality factors.

METHODS

Testing was conducted in 21 healthy volunteers (11 males and 10 females) over a 10-week period using a repeated measures design. Each subject was exposed for 4h to each of the 10 exposure conditions on 10 consecutive working days. The 2-week exposure sequences were randomized, and the exposure to formaldehyde and the effect measurements were conducted in a double-blind fashion. During 4 of the 10 exposure sessions, 12-16 ppm ethyl acetate (EA) was used as a 'masking agent' for formaldehyde exposure. Measurements consisted of conjunctival redness, blinking frequency, nasal flow and resistance, pulmonary function, and reaction times. Also subjective ratings of discomfort as well as the influence of personality factors on the subjective scoring were examined. These were carried out pre-, during and/or post-exposure, and were used to evaluate the possible irritating effects of formaldehyde at these concentrations.

RESULTS

The results indicated no significant treatment effects on nasal flow and resistance, pulmonary function, and reaction times. Blinking frequency and conjunctival redness, ranging from slight to moderate, were significantly increased by short-term peak exposures of 1.0 ppm that occurred at a baseline exposure of 0.5 ppm formaldehyde. Results of the subjective ratings indicated eye and olfactory symptoms at concentrations as low as 0.3 ppm. Nasal irritation was reported at concentration levels of 0.5 ppm plus peaks of 1.0 ppm as well as at levels of 0.3 and 0.5 ppm with co-exposure to EA. However, exposure to EA only was also perceived as irritating. In addition, volunteers who rated their personality as 'anxious' tended to report complaints at a higher intensity. When 'negative affectivity' was used as covariate, the level of 0.3 ppm was no longer an effect level but 0.5 ppm with peaks of 1.0 ppm was. Increased symptom scores were reversed 16 h after the end of the exposures.

CONCLUSIONS

The results of the present study indicated eye irritation as the most sensitive parameter. Minimal objective eye irritation was observed at a level of 0.5 ppm with peaks of 1 ppm. The subjective complaints of ocular and nasal irritation noted at lower levels were not paralleled by objective measurements of eye and nasal irritation and were strongly influenced by personality factors and smell. It was concluded that the no-observed-effect level for subjective and objective eye irritation due to formaldehyde exposure was 0.5 ppm in case of a constant exposure level and 0.3 ppm with peaks of 0.6 ppm in case of short-term peak exposures.