Formaldehyde personal exposure measurements and time weighted exposure estimates in children

Associations between long-term ozone exposure and small airways function in Chinese young adults: a longitudinal cohort study

BACKGROUND

Increasing evidence is appearing that ozone has adverse effects on health. However, the association between long-term ozone exposure and lung function is still inconclusive.

OBJECTIVES

To investigate the associations between long-term exposure to ozone and lung function in Chinese young adults.

METHODS

We conducted a prospective cohort study among 1594 college students with a mean age of 19.2 years at baseline in Shandong, China from September 2020 to September 2021. Lung function indicators were measured in September 2020 and September 2021, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), forced expiratory flow at the 25th, 50th, and 75th percentile of the FVC (FEF25, FEF50, and FEF75) and mean flow rate between 25% and 75% of the FVC (FEF25-75) were measured. Daily 10 km×10 km ozone concentrations come from a well-validated data-fusion approach. The time-weighted average concentrations in 12 months before the lung function test were defined as the long-term ozone exposure. The associations between long-term ozone exposure and lung function indicators in Chinese young adults were investigated using a linear mixed effects model, followed by stratified analyses regarding sex, BMI and history of respiratory diseases.

RESULTS

Each interquartile range (IQR) (8.9 µg/m3) increase in long-term ozone exposure were associated with a -204.3 (95% confidence interval (CI): -361.6, -47.0) ml/s, -146.3 (95% CI: -264.1, -28.4) ml/s, and - 132.8 (95% CI: -239.2, -26.4) ml/s change in FEF25, FEF50, and FEF25-75, respectively. Stronger adverse associations were found in female participants or those with BMI ≥ 24 kg/m2 and history of respiratory diseases.

CONCLUSION

Long-term exposure to ambient ozone is associated with impaired small airway indicators in Chinese young adults. Females, participants with BMI ≥ 24 kg/m2 and a history of respiratory disease have stronger associations.

Personal exposure to aldehydes and potential health risks among schoolchildren in the city

Schoolchildren are sensitive to airborne aldehyde exposures. The knowledge regarding inhalation exposure to aldehydes and the factors influencing exposure in schoolchildren is limited. This study aimed to assess the variability and potential health risks of exposure to aldehydes (including formaldehyde) in schoolchildren. The important factors affecting personal exposure to aldehydes were also explored. Forty schoolchildren were recruited from the urban and suburban areas of Taiwan for aldehyde samplings and questionnaire surveys. Personal and indoor home samples of aldehydes were collected simultaneously during warm and cold seasons. We also identified the potential variables associated with aldehyde exposure based on the participant's responses to the questionnaires using mixed-effects models. The dominant three abundant aldehydes identified in personal exposure samples were formaldehyde (geometric mean, GM = 12.2 µg/m3), acetaldehyde (GM = 5.53 µg/m3), and hexaldehyde (GM = 8.79 µg/m3), accounting for approximately 80% of the total selected aldehydes. Higher personal exposure to aldehydes was observed during the warm season. Moreover, the within-subject variance was predominant, accounting for 66.6 to > 99.9% of the total variance in exposure. Schoolchildren had a high probability of overexposure to formaldehyde and acrolein, which resulted in an incremental lifetime cancer risk of 1.59 × 10-4 (95th percentile = 4.64 × 10-4). Season, location, household refurbishment, and indoor ventilation variables were significantly associated with personal exposure to aldehydes. The results can improve our understanding of aldehyde exposure among schoolchildren to propose mitigation strategies. These findings may be applied to further epidemiological studies.

Relationship between the Young's Moduli of Whole Microcapsules and Their Shell Material Established by Micromanipulation Measurements Based on Diametric Compression between Two Parallel Surfaces and Numerical Modelling

Micromanipulation is a powerful technique to measure the mechanical properties of microparticles including microcapsules. For microparticles with a homogenous structure, their apparent Young's modulus can be determined from the force versus displacement data fitted by the classical Hertz model. Microcapsules can consist of a liquid core surrounded by a solid shell. Two Young's modulus values can be defined, i.e., the one is that determined using the Hertz model and another is the intrinsic Young's modulus of the shell material, which can be calculated from finite element analysis (FEA). In this study, the two Young's modulus values of microplastic-free plant-based microcapsules with a core of perfume oil (hexyl salicylate) were calculated using the aforementioned approaches. The apparent Young's modulus value of the whole microcapsules determined by the classical Hertz model was found to be E_A = 0.095 ± 0.014 GPa by treating each individual microcapsule as a homogeneous solid spherical particle. The previously obtained simulation results from FEA were utilised to fit the micromanipulation data of individual core-shell microcapsules, enabling to determine their unique shell thickness to radius ratio (h/r)_FEA = 0.132 ± 0.009 and the intrinsic Young's modulus of their shell (E_FEA = 1.02 ± 0.13 GPa). Moreover, a novel theoretical relationship between the two Young's modulus values has been derived. It is found that the ratio of the two Young's module values (E_A/E_FEA) is only a function on the ratio of the shell thickness to radius (h/r) of the individual microcapsule, which can be fitted by a third-degree polynomial function of h/r. Such relationship has proven applicable to a broad spectrum of microcapsules (i.e., non-synthetic, synthetic, and double coated shells) regardless of their shell chemistry.

Formaldehyde, Oxidative Stress, and FeNO in Traffic Police Officers Working in Two Cities of Northern Italy

Personal air formaldehyde (air-FA) was measured as risk factor of airways inflammation and oxidative stress (SO) induction. Overall, 154 police officers were enrolled from two differently urbanised Italian cities, Turin and Pavia. Urinary F2t-isoprostane (15-F2t-IsoP), a prostaglandin-like compound, was quantified as a biomarker of general OS in vivo and fractional exhaled nitric oxide (FeNO) was measured for monitoring local inflammatory processes. Urinary cotinine was quantified as a biomarker of tobacco smoking exposure. Traffic police officers living in Turin showed an increased level of log air-FA (p < 0.001), equal to +53.6% (p < 0.001). Log air-(FA) mean values were 3.38 (C.I. 95% 3.33–3.43) and 2.84 (C.I. 95% 2.77–2.92) in Turin and Pavia, respectively. Log (air-FA) was higher in “outdoor workers” (3.18, C.I. 95% 3.13–3.24, p = 0.035) compared to “indoor workers”, showing an increase of +9.3%, even controlling for sex and city. The analyses on 15-F2t-IsoP and FeNO, both adjusted for log air-FA, highlighted that OS and inflammation were higher (+66.8%, p < 0.001 and +75%, p < 0.001, respectively) in Turin traffic police officers compared to those from Pavia. Our findings suggest that even low exposures to traffic-related emissions and urbanisation may influence both general oxidative stress levels and local inflammation.

Maternal Exposure to Indoor Air Pollution and Birth Outcomes

There is a growing body of research on the association between ambient air pollution and adverse birth outcomes. However, people in high income countries spend most of their time indoors. Pregnant women spend much of that time at home. The aim of this study was to investigate if indoor air pollutants were associated with poor birth outcomes. Pregnant women were recruited prior to 18 weeks gestation. They completed a housing questionnaire and household chemical use survey. Indoor pollutants, formaldehyde (HCHO), nitrogen dioxide (NO2) and volatile organic compounds (VOCs), were monitored in the women's homes at 34 weeks gestation. Gestational age (GA), birth weight (BW) and length (BL) and head circumference (HC) were collected from birth records. The associations between measured pollutants, and pollution surrogates, were analysed using general linear models, controlling for maternal age, parity, maternal health, and season of birth. Only HCHO was associated with any of the birth outcomes. There was a 0.044 decrease in BW z-score (p = 0.033) and 0.05 decrease in HC z-score (p = 0.06) for each unit increase in HCHO. Although HCHO concentrations were very low, this finding is consistent with other studies of formaldehyde and poor birth outcomes.

Effect of redox state of Ag on indoor formaldehyde degradation over Ag/TiO2 catalyst at room temperature

Ag/TiO₂ catalysts were prepared via in-situ synthesis and impregnation methods. The effect of redox state of Ag species on catalytic activity of Ag/TiO₂ catalysts was studied. The Ag-i-300 catalyst with partially oxidized state of Ag species shows superior catalytic activity, keeping HCHO removal efficiency at an extraordinary level of 100% during the 200 min's reaction. The Ag/TiO₂ catalysts were characterized by XPS, UV-Vis, BET, XRD, TEM, and in-situ DRIFTS technologies. XPS and TEM results exhibit that the partially oxidized state of Ag^δ+ (0 < δ < 1) and high dispersion of Ag species are beneficial for the oxidation of HCHO over Ag/TiO₂ catalysts. According to the above results, a reaction pathway for HCHO oxidation over Ag-i-300 catalyst was also proposed.

Re-evaluation of the WHO (2010) formaldehyde indoor air quality guideline for cancer risk assessment

In 2010, the World Health Organization (WHO) established an indoor air quality guideline for short- and long-term exposures to formaldehyde (FA) of 0.1 mg/m3 (0.08 ppm) for all 30-min periods at lifelong exposure. This guideline was supported by studies from 2010 to 2013. Since 2013, new key studies have been published and key cancer cohorts have been updated, which we have evaluated and compared with the WHO guideline. FA is genotoxic, causing DNA adduct formation, and has a clastogenic effect; exposure-response relationships were nonlinear. Relevant genetic polymorphisms were not identified. Normal indoor air FA concentrations do not pass beyond the respiratory epithelium, and therefore FA's direct effects are limited to portal-of-entry effects. However, systemic effects have been observed in rats and mice, which may be due to secondary effects as airway inflammation and (sensory) irritation of eyes and the upper airways, which inter alia decreases respiratory ventilation. Both secondary effects are prevented at the guideline level. Nasopharyngeal cancer and leukaemia were observed inconsistently among studies; new updates of the US National Cancer Institute (NCI) cohort confirmed that the relative risk was not increased with mean FA exposures below 1 ppm and peak exposures below 4 ppm. Hodgkin's lymphoma, not observed in the other studies reviewed and not considered FA dependent, was increased in the NCI cohort at a mean concentration ≥0.6 mg/m3 and at peak exposures ≥2.5 mg/m3; both levels are above the WHO guideline. Overall, the credibility of the WHO guideline has not been challenged by new studies.

Human health risks of formaldehyde indoor levels: An issue of concern

Formaldehyde is a carcinogenic substance for humans. Exposure to formaldehyde may also cause eye and respiratory tract irritation, as well as skin sensitization. The main indoor sources of formaldehyde are wood-pressed products, insulation materials, paints, varnishes, household cleaning products and cigarettes, among others. Although this chemical is a well-known indoor pollutant, data on indoor concentrations of formaldehyde are still scarce in some countries. In February 2014, 10 homes in Catalonia, Spain, were randomly selected to collect indoor (bedroom and living room) and outdoor air samples. Ten additional samples were also collected at different workplaces (e.g., offices, shops, classrooms, etc.). Formaldehyde air levels found in homes ranged from 10.7 to 47.7 μg m(-3), from 9.65 to 37.2 μg m(-3), and from 0.96 to 3.37 μg m(-3) in bedrooms, living rooms, and outdoors, respectively. Meanwhile, at workplaces, indoor air levels ranged from 5.86 to 40.4 μg m(-3). These levels are in agreement with data found in the scientific literature. Non-carcinogenic risks were above the threshold limit (HQ > 1), and carcinogenic risks were not acceptable either (>10(-4)). Despite the current study limitations, the results confirm that formaldehyde indoor levels are a matter of health concern, which must be taken into account by policymakers and regulatory bodies.

The microenvironmental modelling approach to assess children's exposure to air pollution - A review

Exposures to a wide spectrum of air pollutants were associated to several effects on children's health. Exposure assessment can be used to establish where and how air pollutants' exposures occur. However, a realistic estimation of children's exposures to air pollution is usually a great ethics challenge, especially for young children, because they cannot intentionally be exposed to contaminants and according to Helsinki declaration, they are not old enough to make a decision on their participation. Additionally, using adult surrogates introduces bias, since time-space-activity patterns are different from those of children. From all the different available approaches for exposure assessment, the microenvironmental (ME) modelling (indirect approach, where personal exposures are estimated or predicted from microenvironment measurements combined with time-activity data) seemed to be the best to assess children's exposure to air pollution as it takes into account the varying levels of pollution to which an individual is exposed during the course of the day, it is faster and less expensive. Thus, this review aimed to explore the use of the ME modelling approach methodology to assess children's exposure to air pollution. To meet this goal, a total of 152 articles, published since 2002, were identified and titles and abstracts were scanned for relevance. After exclusions, 26 articles were fully reviewed and main characteristics were detailed, namely: (i) study design and outcomes, including location, study population, calendar time, pollutants analysed and purpose; and (ii) data collection, including time-activity patterns (methods of collection, record time and key elements) and pollution measurements (microenvironments, methods of collection and duration and time resolution). The reviewed studies were from different parts of the world, confirming the worldwide application, and mostly cross-sectional. Longitudinal studies were also found enhancing the applicability of this approach. The application of this methodology on children is different from that on adults because of data collection, namely the methods used for collecting time-activity patterns must be different and the time-activity patterns are itself different, which leads to select different microenvironments to the data collection of pollutants' concentrations. The most used methods to gather information on time-activity patterns were questionnaires and diaries, and the main microenvironments considered were home and school (indoors and outdoors). Although the ME modelling approach in studies to assess children's exposure to air pollution is highly encouraged, a validation process is needed, due to the uncertainties associated with the application of this approach.

Ocular injury by transient formaldehyde exposure in a rabbit eye model

Formaldehyde (FA) is frequently used in sterilizing surgical instruments and materials. Exposure to FA is highly concerned for eye tissues. Rabbit corneal epithelial cells were examined for changes after FA exposure. Our results showed that cell survival decreased 7 days after transient 3 min exposure to more than 100 ppm FA by trypan blue staining while MTT assay detected significant decrease at 20 ppm at 24 hours observation. The decrease of cell survival rate was concentration (up to 600 ppm)- and observation time (1–7 day)- dependent. The cell number decreased after 100 ppm FA exposure for more than 10 min at 7-day observation. The FA treated cells showed increased apoptosis/necrosis and cell cycle accumulation at sub G1 phase as well as mitochondria clustering around nucleus. The in vivo rabbit eye exposure for tear production by Schirmer’s test revealed that the FA-induced overproduction of tear also exhibited observation time (1–10 day)- and FA concentration (20–300 ppm for 5 min exposure)-dependent. Activated extracellular signal-regulated kinase (pERK2) in cornea explants by western blotting was reduced and increased c-Jun amino - terminal kinase (JNK) activation (pJNK) in cornea and conjunctiva was evident at 2 month after exposure to 50–200 ppm FA for 5 min. In conclusion, injury to the eye with transient exposure of up to 100 ppm FA for 3 min decreased corneal cell survival while a more sensitive MTT test detected the cell decrease at 20 ppm FA exposure. Morphology changes can be observed even at 5 ppm FA exposure for 3 min at 7 days after. The FA exposure also increased apoptotic/necrotic cells and sub-G1 phase in cell cycle. Long term effect (2 months after exposure) on the eye tissues even after the removal of FA can be observed with persistent JNK activation in cornea and conjunctiva.