Formaldehyde and acetaldehyde exposure and risk characterization in California early childhood education environments

Health risk assessment from inhalation exposure to indoor formaldehyde: A systematic review and meta-analysis

This systematic review and meta-analysis investigated studies on formaldehyde (FA) inhalation exposure in indoor environments and related carcinogenic (CR) and non-carcinogenic (HQ) risk. Studies were obtained from Scopus, PubMed, Web of Science, Medline, and Embase databases without time limitation until November 21, 2023. Studies not meeting the criteria of Population, Exposure, Comparator, and Outcomes (PECO) were excluded. The 45 articles included belonged to the 5 types of sites: dwelling environments, educational centers, kindergartens, vehicle cabins, and other indoor environments. A meta-analysis determined the average effect size (ES) between indoor FA concentrations, CR, and HQ values in each type of indoor environment. FA concentrations ranged from 0.01 to 1620 μg/m3. The highest FA concentrations were stated in water pipe cafés and the lowest in residential environments. In more than 90% of the studies uncertain (1.00 ×10-6 1.00 ×10-4) due to FA inhalation exposure was reported and non-carcinogenic risk was stated acceptable. The meta-analysis revealed the highest CR values due to inhalation of indoor FA in high-income countries. As 90% of the time is spent indoors, it is crucial to adopt effective strategies to reduce FA concentrations, especially in kindergartens and schools, with regular monitoring of indoor air quality.

Efficient Exciton Dissociation on Ceria Chelated Cerium-Based MOF Isogenous S-Scheme Photocatalyst for Acetaldehyde Purification

Long-term exposure to low concentration indoor VOCs of acetaldehyde (CH3 CHO) is harmful to human health. Thus, a novel isogenous heterojunction CeO2 /Ce-MOF photocatalyst is synthesized via a one-step hydrothermal method for the effective elimination of CH3 CHO in this work. This CeO2 /Ce-MOF photocatalyst performs well in CH3 CHO removal and achieves an apparent quantum efficiency of 7.15% at 420 nm, which presents ≈6.7 and 3.4 times superior to those generated by CeO2 and Ce-MOF, respectively. The enhanced efficiency is due to two main aspects including i) an effective photocarrier separation ability and the prolonged reaction lifetime of excitons play crucial roles and ii) the formation of an internal electric field (IEF) is sufficient to overcome the considerable exciton binding energy, and increases the exciton dissociation efficiency by up to 50.4%. Moreover, the reasonable pathways and mechanisms of CH3 CHO degradation are determined by in situ DRIFTS analysis and simulated DFT calculations. Those results demonstrated that S-scheme heterojunction successfully increases the efficiency of harmful volatile organic compounds elimination, and it offers essential guidance for designing rare earth-based MOF photocatalysts.

Early Childcare and Education in a Post-Industrial Landscape: Inequalities in Proximity to Active and Relic Manufacturing in Metropolitan Providence, Rhode Island

Children are uniquely vulnerable to environmental health risks associated with industrial contamination, and early childcare and education (ECE) facilities are important sites for potential exposure to environmental contaminants. Emerging research on historic urban industry has additionally demonstrated that urban environmental risk accumulates historically and spatially across urban landscapes. Accordingly, this study pairs cross-sectional data on licensed childcare facilities with longitudinal manufacturing site data in Providence, Rhode Island. We use these data to investigate the proximity of ECE facilities to active and relic manufacturing sites, controlling for a range of organizational- and tract-level characteristics. Results show that type of childcare facility (center-based vs. in-home) and language of instruction (Spanish vs. English) are important predictors of children's proximity to industrial lands, past and present. These findings indicate that Spanish-speaking children in Providence may experience a "double jeopardy" in the form of disproportionate legacy environmental hazards at ECE as well as at home-suggesting that the historical nature of urban industrial land use is an important mechanism of environmental inequality for young children.

Recent Progress and Perspectives of Direct Ink Writing Applications for Mass Transfer Enhancement in Gas-Phase Adsorption and Catalysis

Conventional adsorbents and catalysts shaped by granulation or extrusion have high pressure drop and poor flexibility for chemical, energy, and environmental processes. Direct ink writing (DIW), a kind of 3D printing, has evolved into a crucial technique for manufacturing scalable configurations of adsorbents and catalysts with satisfactory programmable automation, highly optional materials, and reliable construction. Particularly, DIW can generate specific morphologies required for excellent mass transfer kinetics, which is essential in gas-phase adsorption and catalysis. Here, DIW methodologies for mass transfer enhancement in gas-phase adsorption and catalysis, covering the raw materials, fabrication process, auxiliary optimization methods, and practical applications are comprehensively summarized. The prospects and challenges of DIW methodology in realizing good mass transfer kinetics are discussed. Ideal components with a gradient porosity, multi-material structure, and hierarchical morphology are proposed for future investigations.

Indoor formaldehyde levels in residences, schools, and offices in China in the past 30 years: A systematic review

Exposure to formaldehyde causes a variety of adverse health outcomes, while the distributions of indoor formaldehyde in different building types are still not clear in China. In this study, based on the systematic review of previously published data and Monte Carlo simulation, we assessed geographical and temporal distributions of indoor formaldehyde concentrations in residences, schools, and offices across China. A total of 397 studies covered 34 provincial-level regions since 1986 were collected. The results showed that indoor formaldehyde concentrations in residences, schools, and offices in nationwide were decreasing over years due to the publishment of indoor air quality standards since 2002. During 2011 to 2015, the median concentrations of indoor formaldehyde in newly renovated residences, schools, and offices were 153 μg/m³ , 163 μg/m³ , and 94 μg/m³ , with an exceeding rate of 82%, 46%, and 91% considering a standard threshold of 100 μg/m³ at that time, while the exceeding rate was less than 5% for buildings that were renovated beyond one year. Our findings release the temporal trends and geographic distributions of indoor formaldehyde concentrations in residences, schools, and offices in China in the past 30 years, and provide basic data for the comprehensive evaluation of disease burden attributable to indoor formaldehyde exposure.

Evaluation of air quality in indoor and outdoor environments: Impact of anti-COVID-19 measures

This study monitors the presence of 88 volatile organic compounds (VOCs) and semi-volatile organic compounds (semi-VOCs) at the gas phase of seven indoor settings in a school in the city of Tarragona, Spain, and five outdoor locations around the city. The VOCs and semi-VOCs monitored were solvents (∑Solvents), aldehydes (∑Aldehydes), emerging organic compounds (∑EOCs), and other VOCs and semi-VOCs (∑Others). Passive sampling campaigns were performed using Carbopack X tubes followed by thermal desorption coupled to gas chromatography with mass spectrometry (TD-GC-MS). Overall, 70 of the target compounds included in the method were determined in the indoor air samples analysed, and 42 VOCs and semi-VOCs in the outdoor air samples. Our results showed that solvents were ubiquitous throughout the school at concentrations ranging from 272 μg m^-3 to 423 μg m^-3 and representing 68%-83% of total target compounds (∑Total). The values of ∑Total in 2021 were three times as high as those observed at the same indoor settings in 2019, with solvents experiencing the greatest increase. A plausible explanation for these observations is the implementation of anti-COVID-19 measures in the indoor settings, such as the intensification of cleaning activities and the use of hydroalcoholic gels as personal hygiene. The ∑Total values observed in the indoor settings evaluated were twenty times higher than those found outdoors. ∑Solvents were the most representative compounds found indoors (74% of the ∑Total). The concentrations of VOCs and semi-VOCs observed in the outdoors were strictly related to combustion processes from automobile traffic and industrial activities, with ∑Others contributing 58%, ∑Solvents 31%, and ∑Aldehydes 11% of the ∑Total. EOCs, on the other hand, were not detected in any outdoor sample.

Adsorption film with sub-milli-interface morphologies via direct ink writing for indoor formaldehyde removal

In-situ thermally regenerated flexible adsorption films are superior for long-term purification of indoor low-concentration volatile organic compounds (VOCs). To further improve the adsorption kinetics of the films, the surface morphology of adsorption films was suggested in hierarchical channel structure. However, such structure is far from practical applications because of its complicated fabrication method and limited flexibility. In this study, we proposed a convenient and fast method named direct ink writing (DIW) based 3D printing to fabricate flexible adsorption films. Inks were prepared to have appropriate rheological properties and good printability. Three types of adsorption film (flat, straight finned, and trough-like finned) were constructed on flexible polyimide circuit substrates by DIW. We utilized the printed adsorption films for indoor level (1 ppm) formaldehyde removal. The trough-like finned film achieved the best performance among the three printed films, showing a 275% longer penetration time and 252% larger effective adsorption capacity than the flat film. By conducting a 7-cycle adsorption-desorption experiment (more than 12 h), we verified that the films' adsorption performance could effectively recover via in-situ heating. This work could dance around the complicated coating process, increase the structural flexibility and reduce the adsorbent interfacial modification cost.

Formaldehyde, aliphatic aldehydes (C2 -C11 ), furfural, and benzaldehyde in the residential indoor air of children and adolescents during the German Environmental Survey 2014-2017 (GerES V)

Indoor air concentrations of formaldehyde, furfural, benzaldehyde, and 11 aliphatic aldehydes (C₂ -C₁₁ ) were measured in residences of 639 participants in the German Environmental Survey for Children and Adolescents 2014-2017 (GerES V). Sampling was conducted using passive samplers over periods of approximately seven days for each participant. The most abundant compounds were formaldehyde and hexanal with median concentrations of 24.9 µg m^-3 and 10.9 µg m^-3 , respectively. Formaldehyde concentrations exceeded the Guide Value I recommended by the German Committee on Indoor Guide Values (Ausschuss für Innenraumrichtwerte - AIR) (0.10 mg m^-3 ) for 0.3% of the participating residences. The sum of aliphatic n-aldehydes between C₄ (butanal) and C₁₁ (undecanal) exceeded their Guide Value (0.10 mg m^-3 ) for 2.0% of the residences. The geometric mean concentrations of most aldehydes were lower than in the earlier GerES IV (2003-2006) study. Formaldehyde and hexanal concentrations, however, were comparable in both studies and showed no significant difference. Indoor aldehyde concentrations did not exhibit significant correlations with factors collected in questionnaires, such as the age of the participants, their socio-economic status, the location of the residence (former East/West Germany), migration background, tobacco exposure, and the type of furniture used. The validity of the passive sampler measurements was verified against active sampling techniques in a test chamber experiment.

Health risk assessment of volatile organic compounds at daycare facilities

Children are particularly vulnerable to many classes of the volatile organic compounds (VOCs) detected in indoor environments. The negative health impacts associated with chronic and acute exposures of the VOCs might lead to health issues such as genetic damage, cancer, and disorder of nervous systems. In this study, 40 VOCs including aldehydes and ketones, aliphatic hydrocarbons, esters, aromatic hydrocarbons, cyclic terpenes, alcohols, and glycol ethers were identified and qualified in different locations at the University of Missouri (MU) Child Development Laboratory (CDL) in Columbia, Missouri. Our results suggested that the concentrations of the VOCs varied significantly among classrooms, hallways, and playground. The VOCs emitted from personal care and cleaning products had the highest indoor levels (2-ethylhexanol-1, 3-carene, homomenthyl salicylate with mean concentration of 5.15 µg/m³ , 1.57 µg/m³ , and 1.47 µg/m³ , respectively). A cancer risk assessment was conducted, and none of the 95th percentile dose estimates exceeded the age-specific no significant risk levels (NSRL) in all classrooms. Dimensionless toxicity index scores were calculated for all VOCs using a novel web-based framework called Toxicological Prioritization Index (ToxPi), which integrates multiple sources of toxicity data. According to the method, homomenthyl salicylate, benzothiazole, 2-ethylhexyl salicylate, hexadecane, and tridecane exhibited diverse toxicity profiles and ranked as the five most toxic indoor VOCs. The findings of this study provide critical information for policy makers and early education professionals to mitigate the potentially negative health impacts of indoor VOCs in the childcare facilities.

Vertical macro-channel modification of a flexible adsorption board with in-situ thermal regeneration for indoor gas purification to increase effective adsorption capacity

Adsorption has been used widely to remove indoor volatile organic compounds (VOCs). However, the large diffusion resistance inside traditional granular adsorbents renders a low VOC adsorption rate. This study proposes a modified method to achieve the rapid diffusion into the adsorbent during the initial adsorption period. A thin and flexible adsorption board with a layer of adsorbent coated on a heating film was prepared for in-situ adsorption and regeneration. Then, regular, vertical macro-channels through the adsorption board were fabricated by laser drilling to enhance mass transfer inside the board. Experimental results demonstrated that after modification, the penetration times for formaldehyde and xylene extended from 3.8 to 6.2 h, and from 62 to 99 h, respectively. The effective adsorption capacity of the modified board had increased by a multiple of two for formaldehyde and 1.8 for xylene. A mathematical model was developed and experimentally validated to evaluate the modification effect for more adsorbent-pollutant pairs. The results showed that the amplification of effective adsorption capacity was positively correlated with the Da/(K·De) parameter; this is the diffusion resistance ratio prior to and following the modification. A spectrogram of adsorbent-pollutant pairs was plotted to guide the modification. This simple macro-channel modification of the adsorption board may be used as an alternative design for adsorption applications in indoor air purification.

Occupational exposure and health risks of volatile organic compounds of hotel housekeepers: Field measurements of exposure and health risks

Hotel housekeepers represent a large, low-income, predominantly minority, and high-risk workforce. Little is known about their exposure to chemicals, including volatile organic compounds (VOCs). This study evaluates VOC exposures of housekeepers, sources and factors affecting VOC levels, and provides preliminary estimates of VOC-related health risks. We utilized indoor and personal sampling at two hotels, assessed ventilation, and characterized the VOC composition of cleaning agents. Personal sampling of hotel staff showed a total target VOC concentration of 57 ± 36 µg/m3 (mean ± SD), about twice that of indoor samples. VOCs of greatest health significance included chloroform and formaldehyde. Several workers had exposure to alkanes that could cause non-cancer effects. VOC levels were negatively correlated with estimated air change rates. The composition and concentrations of the tested products and air samples helped identify possible emission sources, which included building sources (for formaldehyde), disinfection by-products in the laundry room, and cleaning products. VOC levels and the derived health risks in this study were at the lower range found in the US buildings. The excess lifetime cancer risk (average of 4.1 × 10-5 ) still indicates a need to lower exposure by reducing or removing toxic constituents, especially formaldehyde, or by increasing ventilation rates.

Using low cost open-face passive samplers to sample PM concentration and elemental composition in childcare facilities

Effective, low noise and low-cost samplers for airborne particulate matter (PM) in indoor environments are needed. In 15 northern California childcare facilities, we deployed open-faced polycarbonate substrate passive aerosol samplers and analyzed them using computer-controlled scanning electron microscopy to measure indoor PM particle size, number, and elemental concentration. Particle concentrations were compared to PM concentrations measured by filter-based active samplers. The PM mass concentrations measured after open-faced passive sampling were in good agreement with the PM concentrations obtained using co-located active samplers. The measured PM2.5 concentrations inside of the childcare facilities were in the range of 6-31 μg m-3, while the PM10 concentrations were in the range of 17-96 μg m-3. For PM10, 93.3% of the passive sampler results were within ±30% of those determined with the active sampler, and 67% of the PM2.5 results fell within ±30% of the active sampler measurements. The Pearson's correlation coefficient between PM mass concentrations estimated from the open-faced passive aerosol sampler (OPS) versus gravimetric (active sampler) methods was 0.77 for PM2.5 and 0.95 for PM10, respectively, indicating a strong correlation between the passive and active sampler results. PM and elemental composition varied by facility location and interior characteristics of the childcare facilities such as floor type, presence of combustion sources, occupant density, and the level of activity. The rich carbon content in the polycarbonate substrate produced positive bias in the carbon concentration analysis. Based on the carbon concentration, determined using a copper substrate, a correction factor was needed to determine the total carbon concentrations in the sampled PM for the polycarbonate substrate passive sampler. Overall, the results demonstrated that the OPS collected enough aerosol particles in one business day (6-8 hours) to assess PM levels.

Formaldehyde as an alternative to antibiotics for treatment of refractory impetigo and other infectious skin diseases

Introduction: Antibiotic-resistant strains of bacteria are an increasing problem in hospitals and in the community. This has resulted in bacterial infections such as impetigo becoming difficult to treat. Alternative treatment options are needed. Areas covered: In this paper, a past study that assessed the health burden of scabies in North Queensland is described and from it, the potential for formaldehyde as an alternative antimicrobial treatment is discussed. In doing so, antibiotic resistance, impetigo, permethrin, and formaldehyde are introduced and the current understanding and limitations of the effects of formaldehyde on humans are outlined. The limited cases of formaldehyde resistance in bacteria are also discussed. Expert opinion: Formaldehyde is currently used as a preservative in cosmetics and medicinal creams due to its antibacterial activity. It, therefore, has the potential to be used as an alternative antibacterial treatment for infections with antibiotic-resistant bacteria. The harmful side effects of airborne formaldehyde and exposure in allergic individuals have been extensively studied. Significantly less research has been conducted on formaldehyde skin contact in healthy individuals. If formaldehyde is safe for topical use in humans, it has the potential to assist with combating antibiotic resistance.

Occupational exposure to volatile organic compounds and health risks in Colorado nail salons

Nail salon technicians face chronic exposure to volatile organic compounds (VOCs), which can lead to adverse health outcomes including cancer. In this study, indoor levels of formaldehyde, as well as benzene, toluene, ethylbenzene and xylene, were measured in 6 Colorado nail salons. Personal exposure VOC measurements and health questionnaires (n = 20) were also performed; questionnaires included employee demographics, health symptoms experienced, and protective equipment used. Cancer slope factors from the United States Environmental Protection Agency (US EPA) and anthropometric data from the Centers for Disease Control and Prevention were then used to estimate cancer risk for workers, assuming 20-yr exposures to concentrations of benzene and formaldehyde reported here. Results show that 70% of surveyed workers experienced at least one health issue related to their employment, with many reporting multiple related symptoms. Indoor concentrations of formaldehyde ranged from 5.32 to 20.6 μg m^-3, across all 6 salons. Indoor concentrations of toluene ranged from 26.7 to 816 μg m^-3, followed by benzene (3.13-51.8 μg m^-3), xylenes (5.16-34.6 μg m^-3), and ethylbenzene (1.65-9.52 μg m^-3). Formaldehyde levels measured in one salon exceeded the Recommended Exposure Limit from the National Institute for Occupational Safety and Health. Cancer risk estimates from formaldehyde exposure exceeded the US EPA de minimis risk level (1 × 10^-6) for squamous cell carcinoma, nasopharyngeal cancer, Hodgkin's lymphoma, and leukemia; leukemia risk exceeded 1 × 10^-4 in one salon. The average leukemia risk from benzene exposure also exceeded the US EPA de minimis risk level for all demographic categories modeled. In general, concentrations of aromatic compounds measured here were comparable to those measured in studies of oil refinery and auto garage workers. Cancer risk models determined that 20-yr exposure to formaldehyde and benzene concentrations measured in this study will significantly increase worker's risk of developing cancer in their lifetime.

Characteristics and health effects of formaldehyde and acetaldehyde in an urban area in Iran

This study reports a spatiotemporal characterization of formaldehyde and acetaldehyde in the summer and winter of 2017 in the urban area of Shiraz, Iran. Sampling was fulfilled according to EPA Method TO-11 A. The inverse distance weighting (IDW) procedure was used for spatial mapping. Monte Carlo simulations were conducted to evaluate carcinogenic and non-cancer risk owing to formaldehyde and acetaldehyde exposure in 11 age groups. The average concentrations of formaldehyde/acetaldehyde in the summer and winter were 15.07/8.40 μg m-3 and 8.57/3.52 μg m-3, respectively. The formaldehyde to acetaldehyde ratios in the summer and winter were 1.80 and 2.43, respectively. The main sources of formaldehyde and acetaldehyde were photochemical generation, vehicular traffic, and biogenic emissions (e.g., coniferous and deciduous trees). The mean inhalation lifetime cancer risk (LTCR) values according to the Integrated Risk Information System (IRIS) for formaldehyde and acetaldehyde in summer and winter ranged between 7.55 × 10-6 and 9.25 × 10-5, which exceed the recommended value by US EPA. The average LTCR according to the Office of Environmental Health Hazard Assessment (OEHHA) for formaldehyde and acetaldehyde in summer and winter were between 4.82 × 10-6 and 2.58 × 10-4, which exceeds recommended values for five different age groups (Birth to <1, 1 to <2, 2 to <3, 3 to <6, and 6 to <11 years). Hazard quotients (HQs) of formaldehyde ranged between 0.04 and 4.18 for both seasons, while the HQs for acetaldehyde were limited between 0.42 and 0.97.

A review of the impacts of tobacco heating system on indoor air quality versus conventional pollution sources

With the introduction of novel and potentially less polluting nicotine containing products to the market, the impacts of their usage to indoor air quality as opposed to conventional pollution sources must be reviewed and considered. This review study aimed to comparatively analyse changes in indoor air quality as the consequence of tobacco heating system (THS) generated pollution against general indoor air quality in various micro-environments, especially with combustion-based pollution sources present. Indoor concentrations of formaldehyde, acetaldehyde, benzene, toluene, nicotine and PM_2.5 were reviewed and compared; concentrations of other harmful and potentially harmful substances (HPHCs) were discussed. Generally, the usage of THS has been associated with lower or comparable indoor air pollutant concentrations compared against other conventional indoor sources or environments, in most cases distinguishable above background, thus potentially being associated with health effects at prolonged exposures as any other artificial air pollution source. In the controlled environment the use of THS (as well as an electronic cigarette) resulted in the lowest concentrations of formaldehyde, benzene, toluene, PM_2.5, among majority researched pollution sources (conventional cigarettes, waterpipe, incense, mosquito coils). The exposure to significantly higher pollution levels of benzene, toluene, and formaldehyde occurred in public environments, especially transport micro-environments. Such low levels of conventionally-assessed indoor pollutants resulting from the use of new nicotine containing products raise challenges for epidemiological studies of second-hand exposure to THS aerosol in real-life environments.

Ultrafine, fine, and black carbon particle concentrations in California child-care facilities

Although many U.S. children spend time in child care, little information exists on exposures to airborne particulate matter (PM) in this environment, even though PM may be associated with asthma and other respiratory illness, which is a key concern for young children. To address this data gap, we measured ultrafine particles (UFP), PM_2.5 , PM₁₀ , and black carbon in 40 California child-care facilities and examined associations with potential determinants. We also tested a low-cost optical particle measuring device (Dylos monitor). Median (interquartile range) concentrations for indoor UFP, gravimetric PM_2.5 , real-time PM_2.5 , gravimetric PM₁₀ , and black carbon over the course of a child-care day were 14 000 (11 000-29 000) particles/cm³ , 15 (9.6-21) μg/m³ , 15 (11-23) μg/m³ , 48 (33-73) μg/m³ , and 0.43 (0.25-0.65) ng/m³ , respectively. Indoor black carbon concentrations were inversely associated with air exchange rate (Spearman's rho = -.36) and positively associated with the sum of all Gaussian-adjusted traffic volume within a one-kilometer radius (Spearman's rho = .45) (P-values <.05). Finally, the Dylos may be a valid low-cost alternative to monitor PM levels indoors in future studies. Overall, results indicate the need for additional studies examining particle levels, potential health risks, and mitigation strategies in child-care facilities.

Indoor formaldehyde concentrations in urban China: Preliminary study of some important influencing factors

The Huai River and Qingling Mountain divide (H-Q) divide China into north and south with respect to public policies for building construction and operation practises. China's building energy efficiency standard mandates that air exchange rates be 0.5h^-1 north of the H-Q divide and 1h^-1 south of the divide. China's heating policy allows space heating systems only north of the H-Q divide. Consequently, indoor temperature and humidity differ considerably between north and south. A theoretical model using indoor temperature, humidity, and air change rate was developed to predict indoor formaldehyde concentrations. Data for 39 cities were obtained from 42 studies. There was good agreement between the literature and modelling in a theoretical reference room. The United States Environmental Protection Agency (U.S.EPA) model was applied to estimate cancer risk from formaldehyde exposure indoors. The median indoor formaldehyde concentration for renovation ever from 2002 to 2015 in Chinese cities was 125μg/m³, which is higher than the WHO threshold, 100μg/m³. The median indoor formaldehyde concentrations in the north were higher than in the south (0.5 times higher for dwellings renovated within the past year and 0.2 times higher for renovation ever), driven by the much higher northern winter concentrations (40-1320%). The U.S.EPA model predicts that the lifetime formaldehyde related cancer risk for people living north of the H-Q divide is 1.2 times greater than for people living south. This can be partly explained by greater indoor exposure to formaldehyde for Chinese living north of the H-Q divide.

Evaluation of Low-Cost Mitigation Measures Implemented to Improve Air Quality in Nursery and Primary Schools

Indoor air pollution mitigation measures are highly important due to the associated health impacts, especially on children, a risk group that spends significant time indoors. Thus, the main goal of the work here reported was the evaluation of mitigation measures implemented in nursery and primary schools to improve air quality. Continuous measurements of CO₂, CO, NO₂, O₃, CH₂O, total volatile organic compounds (VOC), PM₁, PM_2.5, PM₁₀, Total Suspended Particles (TSP) and radon, as well as temperature and relative humidity were performed in two campaigns, before and after the implementation of low-cost mitigation measures. Evaluation of those mitigation measures was performed through the comparison of the concentrations measured in both campaigns. Exceedances to the values set by the national legislation and World Health Organization (WHO) were found for PM_2.5, PM₁₀, CO₂ and CH₂O during both indoor air quality campaigns. Temperature and relative humidity values were also above the ranges recommended by American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). In general, pollutant concentrations measured after the implementation of low-cost mitigation measures were significantly lower, mainly for CO₂. However, mitigation measures were not always sufficient to decrease the pollutants’ concentrations till values considered safe to protect human health.

VOC exposures in California early childhood education environments

Little information exists about exposures to volatile organic compounds (VOCs) in early childhood education (ECE) environments. We measured 38 VOCs in single-day air samples collected in 2010-2011 from 34 ECE facilities serving California children and evaluated potential health risks. We also examined unknown peaks in the GC/MS chromatographs for indoor samples and identified 119 of these compounds using mass spectral libraries. VOCs found in cleaning and personal care products had the highest indoor concentrations (d-limonene and decamethylcyclopentasiloxane [D5] medians: 33.1 and 51.4 μg/m³, respectively). If reflective of long-term averages, child exposures to benzene, chloroform, ethylbenzene, and naphthalene exceeded age-adjusted "safe harbor levels" based on California's Proposition 65 guidelines (10^-5 lifetime cancer risk) in 71%, 38%, 56%, and 97% of facilities, respectively. For VOCs without health benchmarks, we used information from toxicological databases and quantitative structure-activity relationship models to assess potential health concerns and identified 12 VOCs that warrant additional evaluation, including a number of terpenes and fragrance compounds. While VOC levels in ECE facilities resemble those in school and home environments, mitigation strategies are warranted to reduce exposures. More research is needed to identify sources and health risks of many VOCs and to support outreach to improve air quality in ECE facilities.

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.