Exposure study to examine chemosensory effects of formaldehyde on hyposensitive and hypersensitive males

Formaldehyde and asthma: a plausibility?

Formaldehyde (FA) is a ubiquitous indoor air pollutant emitted from construction, consumer, and combustion-related products, and ozone-initiated reactions with reactive organic volatiles. The derivation of an indoor air quality guideline for FA by World Health Organization in 2010 did not find convincing evidence for bronchoconstriction-related reactions as detrimental lung function. Causal relationship between FA and asthma has since been advocated in meta-analyses of selected observational studies. In this review, findings from controlled human and animal exposure studies of the airways, data of FA retention in the respiratory tract, and observational studies of reported asthma applied in meta-analyses are analyzed together for coherence of direct association between FA and asthma. New information from both human and animal exposure studies are evaluated together with existing literature and assessed across findings from observational studies and associated meta-analyses thereof. Retention of FA in the upper airways is > 90% in agreement with mice exposure studies that only extreme FA concentrations can surpass trachea, travel to the lower airways, and cause mild bronchoconstriction. However, taken together, detrimental lung function effects in controlled human exposure studies have not been observed, even at FA concentrations up 4 ppm (5 mg/m3), and in agreement with controlled mice exposure studies. Typical indoor FA concentrations in public buildings and homes are far below a threshold for sensory irritation in the upper airways, based on controlled human exposure studies, to induce sensory-irritative sensitization nor inflammatory epithelial damage in the airways. Analysis of the observational heterogeneous studies applied in the meta-analyses suffers from several concomitant multifactorial co-exposures, which invalidates a direct association with asthma, thus the outcome of meta-analyses. The evidence of a direct causal relationship between FA and asthma is insufficient from an experimental viewpoint that includes retention data in the upper airways and controlled animal and human exposure studies. Taken together, a coherence of controlled experimental findings with individual observational studies and associated meta-analyses, which suffer from caveats, is absent. Further, lack of identified evidence of FA-IgE sensitization in both experimental studies and observational studies agrees with indoor FA concentrations far below threshold for sensory irritation. The assessment of experimental data with uncontrolled observational studies in meta-analyses is incompatible with a direct causal relationship between FA and asthma or exacerbation thereof due to lack of coherence and plausibility.

Exposure limits for indoor volatile substances concerning the general population: The role of population-based differences in sensory irritation of the eyes and airways for assessment factors

Assessment factors (AFs) are essential in the derivation of occupational exposure limits (OELs) and indoor air quality guidelines. The factors shall accommodate differences in sensitivity between subgroups, i.e., workers, healthy and sick people, and occupational exposure versus life-long exposure for the general population. Derivation of AFs itself is based on empirical knowledge from human and animal exposure studies with immanent uncertainty in the empirical evidence due to knowledge gaps and experimental reliability. Sensory irritation in the eyes and airways constitute about 30-40% of OELs and is an abundant symptom in non-industrial buildings characterizing the indoor air quality and general health. Intraspecies differences between subgroups of the general population should be quantified for the proposal of more 'empirical' based AFs. In this review, we focus on sensitivity differences in sensory irritation about gender, age, health status, and vulnerability in people, based solely on human exposure studies. Females are more sensitive to sensory irritation than males for few volatile substances. Older people appear less sensitive than younger ones. However, impaired defense mechanisms may increase vulnerability in the long term. Empirical evidence of sensory irritation in children is rare and limited to children down to the age of six years. Studies of the nervous system in children compared to adults suggest a higher sensitivity in children; however, some defense mechanisms are more efficient in children than in adults. Usually, exposure studies are performed with healthy subjects. Exposure studies with sick people are not representative due to the deselection of subjects with moderate or severe eye or airway diseases, which likely underestimates the sensitivity of the group of people with diseases. Psychological characterization like personality factors shows that concentrations of volatile substances far below their sensory irritation thresholds may influence the sensitivity, in part biased by odor perception. Thus, the protection of people with extreme personality traits is not feasible by an AF and other mitigation strategies are required. The available empirical evidence comprising age, lifestyle, and health supports an AF of not greater than up to 2 for sensory irritation. Further, general AFs are discouraged for derivation, rather substance-specific derivation of AFs is recommended based on the risk assessment of empirical data, deposition in the airways depending on the substance's water solubility and compensating for knowledge and experimental gaps. Modeling of sensory irritation would be a better 'empirical' starting point for derivation of AFs for children, older, and sick people, as human exposure studies are not possible (due to ethical reasons) or not generalizable (due to self-selection). Dedicated AFs may be derived for environments where dry air, high room temperature, and visually demanding tasks aggravate the eyes or airways than for places in which the workload is balanced, while indoor playgrounds might need other AFs due to physical workload and affected groups of the general population.

Sensory irritation and use of the best available science in setting exposure limits: Issues raised by a scientific panel review of formaldehyde human research studies

As a high production volume chemical with recognized sensory irritation and widespread exposure, the human health risk potential of formaldehyde has been reviewed by many international regulatory agencies and scientific advisory bodies. A scientific panel, the Human Studies Review Board, under the auspices of the EPA's Toxic Substances Control Act (TSCA) program recently reviewed the sensory irritation studies included in the 2022 Draft Integrated Risk Information System (IRIS) Formaldehyde Hazard Assessment in the context of their use in a weight of evidence evaluation of acute inhalation health effects. This panel issued a series of recommendations on the use of these studies for the purposes of calculating exposure limits (e.g., study design preferences; uncertainty adjustment). Considering that these recommendations might reflect topic areas with varying degrees of scientific consensus, this commentary reflects on commonalities and distinctions amongst international formaldehyde exposure limits based on sensory irritation. Notably, each review panel charged with an assessment of the science recommended that no adjustment was needed to account for either exposure duration or human variability. These areas of scientific consensus should be considered as the best available science for the purposes of setting exposure limits in the anticipated TSCA Risk Evaluation on formaldehyde.

Respiratory Effects of Traffic-Related Air Pollution: A Randomized, Crossover Analysis of Lung Function, Airway Metabolome, and Biomarkers of Airway Injury

BACKGROUND

Exposure to traffic-related air pollution (TRAP) has been associated with increased risks of respiratory diseases, but the biological mechanisms are not yet fully elucidated.

OBJECTIVES

Our aim was to evaluate the respiratory responses and explore potential biological mechanisms of TRAP exposure in a randomized crossover trial.

METHODS

We conducted a randomized crossover trial in 56 healthy adults. Each participant was exposed to high- and low-TRAP exposure sessions by walking in a park and down a road with high traffic volume for 4 h in random order. Respiratory symptoms and lung function, including forced expiratory volume in the first second (FEV 1 ), forced vital capacity (FVC), the ratio of FEV 1 to FVC, and maximal mid-expiratory flow (MMEF), were measured before and after each exposure session. Markers of 8-isoprostane, tumor necrosis factor- α (TNF- α ), and ezrin in exhaled breath condensate (EBC), and surfactant proteins D (SP-D) in serum were also measured. We used linear mixed-effects models to estimate the associations, adjusted for age, sex, body mass index, meteorological condition, and batch (only for biomarkers). Liquid chromatography-mass spectrometry was used to profile the EBC metabolome. Untargeted metabolome-wide association study (MWAS) analysis and pathway enrichment analysis using mummichog were performed to identify critical metabolomic features and pathways associated with TRAP exposure.

RESULTS

Participants had two to three times higher exposure to traffic-related air pollutants except for fine particulate matter while walking along the road compared with in the park. Compared with the low-TRAP exposure at the park, high-TRAP exposure at the road was associated with a higher score of respiratory symptoms [2.615 (95% CI: 0.605, 4.626), p = 1.2 × 10 - 2 ] and relatively lower lung function indicators [- 0.075 L (95% CI: - 0.138 , - 0.012 ), p = 2.1 × 10 - 2 ] for FEV 1 and - 0.190 L / s (95% CI: - 0.351 , - 0.029 ; p = 2.4 × 10 - 2 ) for MMEF]. Exposure to TRAP was significantly associated with changes in some, but not all, biomarkers, particularly with a 0.494 -ng / mL (95% CI: 0.297, 0.691; p = 9.5 × 10 - 6 ) increase for serum SP-D and a 0.123 -ng / mL (95% CI: - 0.208 , - 0.037 ; p = 7.2 × 10 - 3 ) decrease for EBC ezrin. Untargeted MWAS analysis revealed that elevated TRAP exposure was significantly associated with perturbations in 23 and 32 metabolic pathways under positive- and negative-ion modes, respectively. These pathways were most related to inflammatory response, oxidative stress, and energy use metabolism.

CONCLUSIONS

This study suggests that TRAP exposure might lead to lung function impairment and respiratory symptoms. Possible underlying mechanisms include lung epithelial injury, inflammation, oxidative stress, and energy metabolism disorders. https://doi.org/10.1289/EHP11139.

Formaldehyde causes an increase in blood pressure by activating ACE/AT1R axis

Previous studies suggest some link between formaldehyde exposure and harmful cardiovascular effects. But whether exposure to formaldehyde can cause blood pressure to rise, and if so, what the underlying mechanism is, remains unclear. In this study, C57BL/6 male mice were exposed to 0.1, 0.5, 2.5 mg/m³ of gaseous formaldehyde for 4 h daily over a three-week period. The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP) and heart rate (HR) of the mice were measured by tail-cuff plethysmography, and any histopathological changes in the target organs of hypertension were investigated. The results showed that exposure to formaldehyde did cause a significant increase in blood pressure and heart rate, and resulted in varying degrees of damage to the heart, aortic vessels and kidneys. To explore the underlying mechanism, a specific inhibitor of angiotensin converting enzyme (ACE) was used to block the ACE/AT1R axis. We observed the levels of ACE and angiotensin II type 1 receptor (AT1R), as well as the bradykinin (BK) in cardiac cytoplasm. The data suggest that exposure to formaldehyde induced an increase in the expression of ACE and AT1R, and decreased the levels of BK. Strikingly, treatment with 5 mg/kg/d ACE inhibitor can attenuate the increase in blood pressure and the pathological changes caused by formaldehyde exposure. This result has improved our understanding of whether, and how, formaldehyde exposure affects the development of hypertension.

A review of plants formaldehyde metabolism: Implications for hazardous emissions and phytoremediation

The wide use of hazardous formaldehyde (CH₂O) in disinfections, adhesives and wood-based furniture leads to undesirable emissions to indoor environments. This is highly problematic as formaldehyde is a highly hazardous and toxic compound present in both liquid and gaseous form. The majority of gaseous and atmospheric formaldehyde derive from microbial and plant decomposition. However, plants also reversibly absorb formaldehyde released from for example indoor structural materials in such as furniture, thus offering beneficial phytoremediation properties. Here we provide the first comprehensive review of plant formaldehyde metabolism, physiology and remediation focusing on release and absorption including species-specific differences for maintaining indoor environmental air quality standards. Phytoremediation depends on rhizosphere, temperature, humidity and season and future indoor formaldehyde remediation therefore need to take these biological factors into account including the balance between emission and phytoremediation. This would pave the road for remediation of formaldehyde air pollution and improve planetary health through several of the UN Sustainable Development Goals.

Oxidative damage, inflammation, genotoxic effect, and global DNA methylation caused by inhalation of formaldehyde and the purpose of melatonin

Formaldehyde (FA) exposure has been proven to increase the risk of asthma and cancer. This study aimed to evaluate for 28 days the FA inhalation effects on oxidative stress, inflammation process, genotoxicity, and global DNA methylation in mice as well as to investigate the potential protective effects of melatonin. For that, analyses were performed on lung, liver and kidney tissues, blood, and bone marrow. Bronchoalveolar lavage was used to measure inflammatory parameters. Lipid peroxidation (TBARS), protein carbonyl (PCO), non-protein thiols (NPSH), catalase activity (CAT), comet assay, micronuclei (MN), and global methylation were determined. The exposure to 5-ppm FA resulted in oxidative damage to the lung, presenting a significant increase in TBARS and NO levels and a decrease in NPSH levels, besides an increase in inflammatory cells recruited for bronchoalveolar lavage. Likewise, in the liver tissue, the exposure to 5-ppm FA increased TBARS and PCO levels and decreased NPSH levels. In addition, FA significantly induced DNA damage, evidenced by the increase of % tail moment and MN frequency. The pretreatment of mice exposed to FA applying melatonin improved inflammatory and oxidative damage in lung and liver tissues and attenuated MN formation in bone marrow cells. The pulmonary histological study reinforced the results observed in biochemical parameters, demonstrating the potential beneficial role of melatonin. Therefore, our results demonstrated that FA exposure with repeated doses might induce oxidative damage, inflammatory, and genotoxic effects, and melatonin minimized the toxic effects caused by FA inhalation in mice.

Formaldehyde toxicity reports from in vitro and in vivo studies: a review and updated data

Formaldehyde (FA) is a xenobiotic air pollutant and its universal distribution causes a widespread exposure to humans. This review aimed to bring updated information concerning FA toxicity in humans and animals based on in vitro and in vivo studies from 2013 to 2019. Researches were carried out in Pubmed, Scopus, and Science Direct databases to determine the effects of FA exposure on inflammation, oxidative stress and genotoxicity in experimental studies with animals (rats and mice) and humans. Besides, in vitro studies assessing FA cytotoxicity focusing on cell viability and apoptosis in different cell line cultures were reviewed. Studies with humans gave evidence regarding significant deleterious effects on health associated to chronic FA occupational exposure. Evaluations carried out in experimental studies showed toxic effects on different organs as lung, upper respiratory tract, bone marrow and brain as well as in cells. In summary, this study demonstrates that knowing the mechanisms underlying FA toxicity is essential to understand the deleterious effects that this xenobiotic causes on biological systems.

Considerations for refining the risk assessment process for formaldehyde: Results from an interdisciplinary workshop

Anticipating the need to evaluate and integrate scientific evidence to inform new risk assessments or to update existing risk assessments, the Formaldehyde Panel of the American Chemistry Council (ACC), in collaboration with the University of North Carolina, convened a workshop: "Understanding Potential Human Health Cancer Risk - From Data Integration to Risk Evaluation" in October 2017. Twenty-four (24) invited-experts participated with expertise in epidemiology, toxicology, science integration and risk evaluation. Including members of the organizing committee, there were 29 participants. The meeting included eleven presentations encompassing an introduction and three sessions: (1) "integrating the formaldehyde science on nasal/nasopharyngeal carcinogenicity and potential for causality"; (2) "integrating the formaldehyde science on lymphohematopoietic cancer and potential for causality; and, (3) "formaldehyde research-data suitable for risk assessment". Here we describe key points from the presentations on epidemiology, toxicology and mechanistic studies that should inform decisions about the potential carcinogenicity of formaldehyde in humans and the discussions about approaches for structuring an integrated, comprehensive risk assessment for formaldehyde. We also note challenges expected when attempting to reconcile divergent results observed from research conducted within and across different scientific disciplines - especially toxicology and epidemiology - and in integrating diverse, multi-disciplinary mechanistic evidence.

The mystery of dry indoor air - An overview

"Dry air" is a major and abundant indoor air quality complaint in office-like environments. The causality of perceived "dry air" and associated respiratory effects continues to be debated, despite no clear definition of the complaint, yet, has been provided. The perception of "dry air" is semantically confusing without an associated receptor but mimics a proto-state of sensory irritation like a cooling sensation. "Dry air" may also be confused with another common indoor air quality complaint "stuffy air", which mimics the sense of no fresh air and of nasal congestion. Low indoor air humidity (IAH) was dismissed more than four decades ago as cause of "dry air" complaints, rather indoor pollutants was proposed as possible exacerbating causative agents during the cold season. Many studies, however, have shown adverse effects of low IAH and beneficial effects of elevated IAH. In this literature overview, we try to answer, "What is perceived "dry air" in indoor environments and its associated causalities. Many studies have shown that the perception is caused not only by extended exposure to low IAH, but also simultaneously with and possibly exacerbated by indoor air pollutants that aggravate the protective mucous layer in the airways and the eye tear film. Immanent diseases in the nose and airways in the general population may also contribute to the overall complaint rate and including other risk factors like age of the population, use of medication, and external factors like the local ambient humidity. Low IAH may be the single cause of perceived "dry air" in the elderly population, while certain indoor air pollutants may come into play among susceptible people, in addition to baseline contribution of nasal diseases. Thus, perceived "dry air" intercorrelates with dry eyes and throat, certain indoor air pollutants, ambient humidity, low IAH, and nasal diseases.

Effects by inhalation of abundant fragrances in indoor air - An overview

Odorous compounds (odors) like fragrances may cause adverse health effects. To assess their importance by inhalation, we have reviewed how the four major abundant and common airborne fragrances (α-pinene (APN), limonene (LIM), linalool (LIL), and eugenol (EUG)) impact the perceived indoor air quality as odor annoyance, sensory irritation and sensitization in the airways. Breathing and cardiovascular effects, and work performance, and the impact in the airways of ozone-initiated gas- and particle phase reactions products have also been assessed. Measured maximum indoor concentrations for APN, LIM and LIL are close to or above their odor thresholds, but far below their thresholds for sensory irritation in the eyes and upper airways; no information could be traced for EUG. Likewise, reported risk values for long-term effects are far above reported indoor concentrations. Human exposure studies with mixtures of APN and LIM and supported by animal inhalation models do not support sensitization of the airways at indoor levels by inhalation that include other selected fragrances. Human exposure studies, in general, indicate that reported lung function effects are likely due to the perception rather than toxic effects of the fragrances. In general, effects on the breathing rate and mood by exposure to the fragrances are inconclusive. The fragrances may increase the high-frequency heart rate variability, but aerosol exposure during cleaning activities may result in a reduction. Distractive effects influencing the work performance by fragrance/odor exposure are consistently reported, but their persistence over time is unknown. Mice inhalation studies indicate that LIM or its reaction mixture may possess anti-inflammatory properties. There is insufficient information that ozone-initiated reactions with APN or LIM at typical indoor levels cause airway effects in humans. Limited experimental information is available on long-term effects of ozone-initiated reaction products of APN and LIM at typical indoor levels.

External eye symptoms in indoor environments

Eye irritation, for example dry or irritated eyes, is generally among top three reported symptoms in office-like environments, in particular among workplaces with cognitive demanding visual display unit (VDU) work. The symptoms are especially among middle and advanced ages and particularly among women more than men. The symptoms are also among the most commonly reported complaints in the eye clinic. To be in a position to interpret the high prevalence of eye symptoms, a multidisciplinary and integrated approach is necessary that involves the external eye physiology (separate from internal eye effects), eye diseases (evaporative dry eye (DE), aqueous-deficient DE, and gland dysfunctions), and risk factors that aggravate the stability of precorneal tear film (PTF) resulting in hyperosmolarity and initiation of inflammatory reactions. Indoor environmental, occupational and personal risk factors may aggravate the PTF stability; factors such as age, contact lenses, cosmetics, diet, draft, gender, low humidity and high temperature, medication, outdoor and combustion pollutants, and VDU work. Psychological stressors may further influence the reporting behavior of eye symptoms. The impact of the risk factors may occur in a combined and exacerbating manner.

Assessment of indoor air quality in office buildings across Europe - The OFFICAIR study

The European project OFFICAIR aimed to broaden the existing knowledge regarding indoor air quality (IAQ) in modern office buildings, i.e., recently built or refurbished buildings. Thirty-seven office buildings participated in the summer campaign (2012), and thirty-five participated in the winter campaign (2012-2013). Four rooms were investigated per building. The target pollutants were twelve volatile organic compounds, seven aldehydes, ozone, nitrogen dioxide and particulate matter with aerodynamic diameter <2.5μm (PM_2.5). Compared to other studies in office buildings, the benzene, toluene, ethylbenzene, and xylene concentrations were lower in OFFICAIR buildings, while the α-pinene and d-limonene concentrations were higher, and the aldehyde, nitrogen dioxide and PM_2.5 concentrations were of the same order of magnitude. When comparing summer and winter, significantly higher concentrations were measured in summer for formaldehyde and ozone, and in winter for benzene, α-pinene, d-limonene, and nitrogen dioxide. The terpene and 2-ethylhexanol concentrations showed heterogeneity within buildings regardless of the season. Considering the average of the summer and winter concentrations, the acetaldehyde and hexanal concentrations tended to increase by 4-5% on average with every floor level increase, and the nitrogen dioxide concentration tended to decrease by 3% on average with every floor level increase. A preliminary evaluation of IAQ in terms of potential irritative and respiratory health effects was performed. The 5-day median and maximum indoor air concentrations of formaldehyde and ozone did not exceed their respective WHO air quality guidelines, and those of acrolein, α-pinene, and d-limonene were lower than their estimated thresholds for irritative and respiratory effects. PM_2.5 indoor concentrations were higher than the 24-h and annual WHO ambient air quality guidelines.

Human exposure to acrolein: Time-dependence and individual variation in eye irritation

The aim of the study was to examine the time dependence on sensory irritation detection following exposure to threshold levels of acrolein, in humans. The exposures occurred in an exposure chamber and the subjects were breathing fresh air through a mask that covered the nose and mouth. All participants participated in four exposure conditions, of which three consisted of a mixture of acrolein and heptane and one of only heptane. Exposure to acrolein at a concentration half of the TLV-C lead to sensory irritation. The perceived sensory irritation resulted in both increased detectability and sensory irritation after about 6.8min of exposure in 58% of the participants. The study confirm the previously suggested LOAEL of about 0.34mg/m(3) for eye irritation due to acrolein exposure. The sensory irritation was still significant 10min after exposure. These results have implications for risk assessment and limit setting in occupational hygiene.

Pollutant exposures and health symptoms in aircrew and office workers: Is there a link?

Sensory effects in eyes and airways are common symptoms reported by aircraft crew and office workers. Neurological symptoms, such as headache, have also been reported. To assess the commonality and differences in exposures and health symptoms, a literature search of aircraft cabin and office air concentrations of non-reactive volatile organic compounds (VOCs) and ozone-initiated terpene reaction products were compiled and assessed. Data for tricresyl phosphates, in particular tri-ortho-cresyl phosphate (ToCP), were also compiled, as well as information on other risk factors such as low relative humidity. A conservative health risk assessment for eye, airway and neurological effects was undertaken based on a "worst-case scenario" which assumed a simultaneous constant exposure for 8h to identified maximum concentrations in aircraft and offices. This used guidelines and reference values for sensory irritation for eyes and upper airways and airflow limitation; a tolerable daily intake value was used for ToCP. The assessment involved the use of hazard quotients or indexes, defined as the summed ratio(s) (%) of compound concentration(s) divided by their guideline value(s). The concentration data suggest that, under the assumption of a conservative "worst-case scenario", aircraft air and office concentrations of the compounds in question are not likely to be associated with sensory symptoms in eyes and airways. This is supported by the fact that maximum concentrations are, in general, associated with infrequent incidents and brief exposures. Sensory symptoms, in particular in eyes, appear to be exacerbated by environmental and occupational conditions that differ in aircraft and offices, e.g., ozone incidents, low relative humidity, low cabin pressure, and visual display unit work. The data do not support airflow limitation effects. For ToCP, in view of the conservative approach adopted here and the rareness of reported incidents, the health risk of exposure to this compound in aircraft is considered negligible.

EPHECT III: Health risk assessment of exposure to household consumer products

In the framework of the EU EPHECT project (Emissions, Exposure Patterns and Health Effects of Consumer Products in the EU), irritative and respiratory effects were assessed in relation to acute (30-min) and long-term (24-h) inhalation exposure to key and emerging indoor air pollutants emitted during household use of selected consumer products. A detailed Health Risk Assessment (HRA) was performed for five selected pollutants of respiratory health relevance, namely acrolein, formaldehyde, naphthalene, d-limonene and α-pinene. For each pollutant, the Critical Exposure Limit (CEL) was compared to indoor air concentrations and exposure estimates for the use of 15 selected consumer products by two population groups (housekeepers and retired people) in the four geographical regions of Europe (North, West, South, East), which were derived previously based on microenvironmental modelling. For the present HRA, health-based CELs were derived for certain compounds in case indoor air quality guidelines were not available by the World Health Organization for end-points relevant to the current study. For each pollutant, the highest indoor air concentrations in each microenvironment and exposure estimates across home microenvironments during the day were lower than the corresponding acute and long-term CELs. However, considerable contributions, especially to acute exposures, were obtained in some cases, such as formaldehyde emissions resulting from single product use of a floor cleaning agent (82% CEL), a candle (10% CEL) and an electric air freshener (17% CEL). Regarding multiple product use, the case of 30-min formaldehyde exposure reaching 34% CEL when eight product classes were used across home microenvironments, i.e. all-purpose/kitchen/floor cleaning agents, furniture/floor polish, combustible/electric air fresheners, and perfume, needs to be highlighted. Such estimated values should be evaluated with caution, as these may be attributed to the exposure scenarios specifically constructed for the present study, following a 'most-representative worst-case scenario' approach for exposure and health risk assessment.

Ozone-initiated terpene reaction products in five European offices: replacement of a floor cleaning agent

Cleaning agents often emit terpenes that react rapidly with ozone. These ozone-initiated reactions, which occur in the gas-phase and on surfaces, produce a host of gaseous and particulate oxygenated compounds with possible adverse health effects in the eyes and airways. Within the European Union (EU) project OFFICAIR, common ozone-initiated reaction products were measured before and after the replacement of the regular floor cleaning agent with a preselected low emitting floor cleaning agent in four offices located in four EU countries. One reference office in a fifth country did not use any floor cleaning agent. Limonene, α-pinene, 3-carene, dihydromyrcenol, geraniol, linalool, and α-terpineol were targeted for measurement together with the common terpene oxidation products formaldehyde, 4-acetyl-1-methylcyclohexene (4-AMCH), 3-isopropenyl-6-oxo-heptanal (IPOH), 6-methyl-5-heptene-2-one, (6-MHO), 4-oxopentanal (4-OPA), and dihydrocarvone (DHC). Two-hour air samples on Tenax TA and DNPH cartridges were taken in the morning, noon, and in the afternoon and analyzed by thermal desorption combined with gas chromatography/mass spectrometry and HPLC/UV analysis, respectively. Ozone was measured in all sites. All the regular cleaning agents emitted terpenes, mainly limonene and linalool. After the replacement of the cleaning agent, substantially lower concentrations of limonene and formaldehyde were observed. Some of the oxidation product concentrations, in particular that of 4-OPA, were also reduced in line with limonene. Maximum 2 h averaged concentrations of formaldehyde, 4-AMCH, 6-MHO, and IPOH would not give rise to acute eye irritation-related symptoms in office workers; similarly, 6-AMCH, DHC and 4-OPA would not result in airflow limitation to the airways.

Sensory irritation as a basis for setting occupational exposure limits

There is a need of guidance on how local irritancy data should be incorporated into risk assessment procedures, particularly with respect to the derivation of occupational exposure limits (OELs). Therefore, a board of experts from German committees in charge of the derivation of OELs discussed the major challenges of this particular end point for regulatory toxicology. As a result, this overview deals with the question of integrating results of local toxicity at the eyes and the upper respiratory tract (URT). Part 1 describes the morphology and physiology of the relevant target sites, i.e., the outer eye, nasal cavity, and larynx/pharynx in humans. Special emphasis is placed on sensory innervation, species differences between humans and rodents, and possible effects of obnoxious odor in humans. Based on this physiological basis, Part 2 describes a conceptual model for the causation of adverse health effects at these targets that is composed of two pathways. The first, “sensory irritation” pathway is initiated by the interaction of local irritants with receptors of the nervous system (e.g., trigeminal nerve endings) and a downstream cascade of reflexes and defense mechanisms (e.g., eyeblinks, coughing). While the first stages of this pathway are thought to be completely reversible, high or prolonged exposure can lead to neurogenic inflammation and subsequently tissue damage. The second, “tissue irritation” pathway starts with the interaction of the local irritant with the epithelial cell layers of the eyes and the URT. Adaptive changes are the first response on that pathway followed by inflammation and irreversible damages. Regardless of these initial steps, at high concentrations and prolonged exposures, the two pathways converge to the adverse effect of morphologically and biochemically ascertainable changes. Experimental exposure studies with human volunteers provide the empirical basis for effects along the sensory irritation pathway and thus, “sensory NOAEC_human” can be derived. In contrast, inhalation studies with rodents investigate the second pathway that yields an “irritative NOAEC_animal.” Usually the data for both pathways is not available and extrapolation across species is necessary. Part 3 comprises an empirical approach for the derivation of a default factor for interspecies differences. Therefore, from those substances under discussion in German scientific and regulatory bodies, 19 substances were identified known to be human irritants with available human and animal data. The evaluation started with three substances: ethyl acrylate, formaldehyde, and methyl methacrylate. For these substances, appropriate chronic animal and a controlled human exposure studies were available. The comparison of the sensory NOAEC_human with the irritative NOAEC_animal (chronic) resulted in an interspecies extrapolation factor (iEF) of 3 for extrapolating animal data concerning local sensory irritating effects. The adequacy of this iEF was confirmed by its application to additional substances with lower data density (acetaldehyde, ammonia, n-butyl acetate, hydrogen sulfide, and 2-ethylhexanol). Thus, extrapolating from animal studies, an iEF of 3 should be applied for local sensory irritants without reliable human data, unless individual data argue for a substance-specific approach.

New results on formaldehyde: the 2nd International Formaldehyde Science Conference (Madrid, 19-20 April 2012)

The toxicology and epidemiology of formaldehyde were discussed on the 2nd International Formaldehyde Science Conference in Madrid, 19-20 April 2012. It was noted that a substantial amount of new scientific data has appeared within the last years since the 1st conference in 2007. Progress has been made in characterisation of genotoxicity, toxicokinetics, formation of exogenous and endogenous DNA adducts, controlled human studies and epidemiology. Thus, new research results are now at hand to be incorporated into existing evaluations on formaldehyde by official bodies.

Recent trend in risk assessment of formaldehyde exposures from indoor air

Studies about formaldehyde (FA) published since the guideline of 0.1 mg/m(3) by the World Health Organization (WHO) in 2010 have been evaluated; critical effects were eye and nasal (portal-of-entry) irritation. Also, it was considered to prevent long-term effects, including all types of cancer. The majority of the recent toxicokinetic studies showed no exposure-dependent FA-DNA adducts outside the portal-of-entry area and FA-DNA adducts at distant sites were due to endogenously generated FA. The no-observed-adverse-effect level for sensory irritation was 0.5 ppm and recently reconfirmed in hypo- and hypersensitive individuals. Investigation of the relationship between FA exposure and asthma or other airway effects in children showed no convincing association. In rats, repeated exposures showed no point mutation in the p53 and K-Ras genes at ≤15 ppm neither increased cell proliferation, histopathological changes and changes in gene expression at 0.7 ppm. Repeated controlled exposures (0.5 ppm with peaks at 1 ppm) did not increase micronucleus formation in human buccal cells or nasal tissue (0.7 ppm) or in vivo genotoxicity in peripheral blood lymphocytes (0.7 ppm), but higher occupational exposures were associated with genotoxicity in buccal cells and cultivated peripheral blood lymphocytes. It is still valid that exposures not inducing nasal squamous cell carcinoma in rats will not induce nasopharyngeal cancer or lymphohematopoietic malignancies in humans. Reproductive and developmental toxicity are not considered relevant in the absence of sensory irritation. In conclusion, the WHO guideline has been strengthened.