Indoor Formaldehyde Research Articles

Formaldehyde in residences: long-term indoor concentrations and influencing factors.

Chronic human exposure to formaldehyde is significantly increased by indoor sources. However, information is lacking on why these exposures appear to persist in older homes with aging sources. We use data from the Relationships of Indoor, Outdoor, and Personal Air study to evaluate 179 residences, most of which were older than 5 years. We assess the dependence of indoor formaldehyde concentrations (C(in)) on building type and age, whole-house air exchange rate, indoor temperature, and seasonal changes. Indoor formaldehyde had mean and median concentrations of 17 ppb, and primarily originated from indoor sources. The factors we analyzed did not explain much of the variance in C(in), probably because of their limited influence on mechanisms that control the long-term release of formaldehyde from aging pressed-wood products bound with urea-formaldehyde (UF) resins. We confirmed that the mitigating effects of ventilation on C(in) decrease with time through the analysis of data for new homes available in the literature, and through models. We also explored source control strategies and conclude that source removal is the most effective way to decrease chronic exposures to formaldehyde in existing homes. For new homes, reducing indoor sources and using pressed-wood with lower UF content are likely the best solutions. Formaldehyde concentrations in homes due to indoor sources appear to persist throughout the lifetime of residences. Increases in ventilation rates are most effective in decreasing indoor concentrations in new homes where formaldehyde levels are high or when homes are tight. Consequently, other alternatives need to be promoted such as decreasing the amount of pressed-wood products with urea-formaldehyde (UF) resins in homes or reducing the UF content in these materials.

Reduction of indoor formaldehyde concentration by a photocatalyst fluorescent lamp

Reduction of indoor formaldehyde concentration by a photocatalyst fluorescent lamp

家庭用空気清浄機のホルムアルデヒド除去性能の劣化性に関する研究

家庭用空気清浄機のホルムアルデヒド除去性能の劣化性に関する研究

Validation of a passive flux sampler for on-site measurement of formaldehyde emission rates from building and furnishing materials

A diffusive sampling device was developed for screening indoor sources of formaldehyde and determining the emission rates of these sources on-site. It consists of a glass Petri dish containing a quartz filter coated with 2,4-dinitrophenylhydrazine (DNPH) which is placed on the tested material for sampling. Formaldehyde emitted from the material diffuses through the air column inside the sampler and is collected onto the DNPH filter. The formaldehyde emission rate is determined from the mass collected by the sampler. The dependence of the sampled formaldehyde amount on the diffusion length inside the sampler was examined and led us to select a length of 20 mm for which the diffusion in the air layer controls the mass transfer from the material to the sampling surface (filter). A linear relationship with a high correlation (r2 = 0.97) was obtained between the mass collected by the passive flux sampler and the emission rates measured by a standard chamber method, analysing a large series of indoor materials with the two methods in parallel. Neither the sampling time (ranging from 4 to 8 h) nor the temperature (from 23 to 35 °C) was observed to influence the sampler performance. Furthermore, the detection limit attained 1.2 μg m−2 h−1 for a 6h-sampling time and a satisfying precision of replicate measurements (relative standard deviation of 7.8% on average) is adequate for monitoring the emission rates of primary sources contributing to formaldehyde indoor concentrations.

The gas sensitivity of nano TiO 2–SnO 2 film doped with Cd(II) ion

The nanocomposite oxide (0.2TiO 2–0.8SnO 2) doped with Cd 2+ powder have been prepared and characterized by XRD and their gas-sensing sensitivity were characterized using gas sensing measurement. Experimental results show that, bicomponent nano anatase TiO 2 and rutile SnO 2 particulate thick film doped with Cd 2+ behaves with good sensitivity to formaldehyde gas of 200 ppm in the air, and the optimum sensing temperature was reduced from 360 °C to 320 °C compared with the undoped Cd 2+ thick film. The gas sensing thick films doped with Cd 2+ also show good selectivity to formaldehyde among benzene, toluene, xylene and ammonia as disturbed gas and could be effectively used as an indoor formaldehyde sensor.

Creation of three-dimensionally ordered macroporous Au/CeO2 catalysts with controlled pore sizes and their enhanced catalytic performance for formaldehyde oxidation

Three-dimensionally ordered macroporous (3DOM) Au/CeO2 catalysts with controlled pore sizes are successfully created via a colloidal crystal template method, and their enhanced catalytic performance for formaldehyde oxidation is systematically investigated for the first time in this paper. The resulting Au/CeO2 catalysts possess well-defined 3DOM structures with adjustable pore sizes from 80 to 280nm, having interconnected networks of spherical voids. Due to the uniform macroporous structures leading to good distribution of catalytic species of Au nanoparticles with less aggregation, the 3DOM Au/CeO2 catalysts are expected to have enhanced capability for formaldehyde catalytic oxidation. The formaldehyde oxidation tests reveal that the 3DOM Au/CeO2 catalysts exhibit superior catalytic activity with 100% formaldehyde conversion at ∼75°C, a much lower temperature than previously reported powder Au/CeO2 catalysts. The superior performance of 3DOM Au/CeO2 catalysts for formaldehyde oxidation makes them potentially applicable to in-door formaldehyde decontamination and industrial catalysis.

Formaldehyde and volatile organic compounds in Hong Kong homes: concentrations and impact factors

This paper presents formaldehyde and volatile organic compounds (VOC) concentrations, potential sources and impact factors in 100 homes. The 24-h average formaldehyde concentration in 37 homes exceeded the good class of the Hong Kong Indoor Air Quality Objectives (HKIAQO), whereas the total VOCs concentration in all homes was lower than the HKIAQO. Compared to other East Asian cities, indoor formaldehyde and styrene in Hong Kong was the highest, reflecting that the homes in Hong Kong were more affected by household products and materials. The formaldehyde concentration in newly built apartments was significantly higher than that in old buildings, whereas no relationship between the concentration and the building age was found for VOCs. There was no difference for formaldehyde and toluene between smoking and non-smoking homes, suggesting that cigarette smoking was not the major source of these two species. Homes of a couple with a child had higher formaldehyde and acetic acid concentrations, while homes with more than three people had higher concentrations of 1-butanol, heptane and d-limonene. When shoes were inside the homes, heptane, acetic acid, nonane and styrene concentrations were statistically higher than that when shoes were out of the homes. Furthermore, higher levels of 1,2,4-trimethylbenzene, styrene, nonane and heptane were found in gas-use families rather than in electricity-use homes. Long-term exposure to formaldehyde and volatile organic compounds (VOC) in indoor environments may cause a number of adverse health effects such as asthma, dizziness, respiratory and lung diseases, and even cancers. Therefore, it is critical to minimize indoor air pollution caused by formaldehyde and VOCs. The findings obtained in this study would significantly enhance our understanding on the levels, emission sources and factors which affect indoor concentrations of formaldehyde and VOCs. The results can help housing designers, builders, home residents, and housing department of the government to improve indoor air quality (IAQ) by means of appropriate building materials, clean household products and proper life styles. It can also help policy makers reconcile the IAQ objectives and guidelines.

Surface-catalysed reactions on pollutant-removing building products for indoor use

In order to evaluate the potential for emission of secondary reaction products from building materials designed to remove pollutants from indoor air, four samples of ceiling tiles – three commercially available and one custom-made – were investigated in chamber experiments. The chambers were irradiated with artificial light simulating indoor conditions and formaldehyde as well as several VOCs (2-butanone, n-butanol, toluene, hexanal, n- butylacetate, 2-butoxyethanol, α-pinene, benzaldehyde, n-decane, limonene and 1,2-dichlorobenzene) were added. Depending on the individual substrate–substance combination, it was possible to identify secondary emissions, e.g. formaldehyde, furfural, acetophenone, n-butylbutyrate, n-butyl-i-butyrate, n-butylpropionate, 4-heptanone, acetic acid, i-butyraldehyde and crotonaldehyde. These were generated by cleavage, hydrolysis, rearrangement or radical reactions. Some of these reactions also occurred with samples not containing photocatalysts. All these secondary emissions have to be taken seriously into account when evaluating the performance of materials designed to remove pollutants from indoor air, as they can prove detrimental to human health.

Assessment and predictor determination of indoor aldehyde levels in Paris newborn babies’ homes

Exposure to indoor chemical air pollutants expected to be potentially involved in allergic respiratory diseases in infants is poorly documented. A specific environmental investigation included in a birth cohort study was carried out to first assess indoor airborne aldehyde levels, using passive devices and their variability within 1 year (1, 6, 9 and 12 months) in the bedroom of 196 Paris infants, and second, to identify predictors for aldehyde concentrations using interviewer administered questionnaires about housing factors. Comfort parameters and carbon dioxide levels were measured simultaneously. Aldehydes were detected in almost all dwellings and geometric mean levels (geometric standard deviation) at the first visit were respectively for formaldehyde, acetaldehyde, hexanal, and pentanal 19.4 (1.7) microg/m(3), 8.9 (1.8) microg/m(3), 25.3 (3.1) microg/m(3), 3.7 (2.3) microg/m(3), consistent with earlier published results. Generalized Estimating Equation multivariate analyses showed that, apart from comfort parameters, aeration and season, the main indoor aldehyde sources were either continuous (building materials and coverings especially when they were new) or discontinuous (smoking, use of air fresheners and cleaning products, DIY etc...). Finally, the data collected by questionnaires should be sufficient to enable us to classify each infant in our cohort study according to his/her degree of exposure to the main aldehydes. This analysis contributed to document indoor aldehyde levels in Parisian homes and to identify factors determining these levels. In the major part of newborn babies' homes, indoor formaldehyde levels were above the guideline value of 10 microg/m(3) proposed by the French Agency for Environmental and Occupational Health Safety for long-term exposure. Given this result, it is essential to study the health impact of exposure to aldehydes especially formaldehyde on the incidence of respiratory and allergic symptoms, particularly during the first months of life.

Indoor formaldehyde and acetaldehyde levels in the province of Bari, South Italy, and estimated health risk

Indoor and outdoor formaldehyde and acetaldehyde levels were assessed to characterize pollution in dwellings in the city and the Province of Bari, also taking into account seasonal variability, and to investigate health effects of aldehyde exposure on the general population. In 2007, passive environmental monitoring was performed, for 24 hours, in the kitchen of 59 dwellings, as well as outdoors for 27 of them. A questionnaire probing personal and home characteristics was administered to all 182 subjects habitually resident in the homes. During the period January-June 2008, formaldehyde and acetaldehyde levels were monitored monthly in 20 of the investigated dwellings inhabited only by non smokers. Indoor formaldehyde and acetaldehyde concentrations were significantly higher (16.0 +/- 8.0 and 10.7 +/- 8.8 microg m(-3)) than outdoor concentrations (4.4 +/- 1.7 and 3.4 +/- 2.0 microg m(-3)), showing a correlation between indoor levels of the two aldehydes (r = 0.41; p = 0.001). In dwellings inhabited only by non smokers, formaldehyde concentrations were higher in the presence of furniture bought new or restored less than one year before (p = 0.03). Formaldehyde and acetaldehyde levels were significantly higher in winter months than in spring-summer months (F = 2.86, p = 0.02; F = 5.39, p < 0.001) and seemed to be influenced by the time that kitchen windows were kept open. As regards the effects on human health, a low prevalence of allergic disease and no association between any irritant or allergic complaints and indoor levels of the two aldehydes was observed. In conclusion, the results showed low indoor and outdoor concentrations of formaldehyde and acetaldehyde, not generally posing a risk for human health.

ＤＮＰＨカートリッジによる室内アルデヒドの分析精度の実態調査

In recent years, volatile organic compounds have caused chemical sensitivity by increasing indoor air pollutant concentrations. In order to solve the problem, Ministry of Health, Labour and Welfare of Japanese Government established the guideline values for indoor air concentrations, such as formaldehyde, acetaldehyde, toluene and so on. However it is not clear that accuracy of the measurement method for volatile organic compounds in indoor air is sufficient enough to judge the indoor air quality of the room to the guidelines.This study aimed at investigating precision of the analytical method using DNPH cartridge for indoor formaldehyde and acetaldehyde concentrations. Sample cartridges of the blank, standard and indoor air were prepared. The 5 kinds of DNPH cartridges were used to analyze dispersion of the test results, and the samples for laboratory tests using HPLC were sent to 11 laboratories. Since the CV values were under 20%, the dispersion was not too large. The dispersions found in data were considered to be caused by accuracy of cartridges and analyzing performance of each laboratory. We should recognize that data for indoor concentrations by DNPH cartridge could be fairly dispersed.

An enrichment method to detect low concentration formaldehyde

Abstract A semiconductor gas sensor of tin oxide doped with hydroxyl (OH) functionalized multi-wall carbon nanotubes (MWCNTs) was fabricated for detecting indoor formaldehyde concentration. The response of the MWCNTs-doped SnO2 sensor was much higher than that of an undoped SnO2 sensor. In order to detect low concentration formaldehyde, a novel enrichment method utilizing active carbon was applied. The response of the sensor was obviously increased by the application of the enrichment method. The lowest concentration of formaldehyde gas detected by a 5 wt% MWCNTs-doped SnO2 sensor was 0.03 ppm.

Preparation and gas sensing properties of p-type La-Bi-Fe-O nanorods

La-Bi-Fe-O nanorods were prepared for the first time via a facile hydrothermal method without any surfactant. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize the structure and morphology of the material. The semiconductive La-Bi-Fe-O nanorods are mainly composed of orthorhombic Bi 2Fe 4O 9 and a small amount of orthorhombic La 1.08Bi 0.92O 3.03. The gas sensing properties of the sensor based on La-Bi-Fe-O nanorods were studied and the nanorods exhibited a p-type behavior. Both the sensitivity and selectivity of the sensor towards formaldehyde were very high, and the sensor could be used to detect formaldehyde as low concentration as 5 ppm. More importantly, the operation temperature of the La-Bi-Fe-O sensor was low. This would be very significant in applications, such as detecting and preventing indoor formaldehyde pollution.

Study on a micro-gas sensor with SnO2–NiO sensitive film for indoor formaldehyde detection

Abstract A micro-gas sensor is fabricated based on a micro-hotplate (MHP) with micromachining technology. The SnO 2 –NiO nanometer polycrystalline composite synthesized by a chemical co-precipitation method is coated onto a micro-hotplate as a sensitive film. The response and recovery time of the micro-gas sensor decrease rapidly with increasing the formaldehyde (HCHO) concentration at relatively low concentrations. The micro-gas sensor shows good stability, low power consumption of 180 mW at the MHP operation temperature of 300 °C, and high selectivity in the presence of interference gases such as alcohol, toluene, α-pinene and acetone. The micro-gas sensor can detect 0.06 ppm HCHO, which is the indoor exposure limit for HCHO referring to Chinese environmental protection agency (EPA).

Energy impact assessment for the reduction of carbon dioxide and formaldehyde exposure risk in air-conditioned offices

Treatment of fresh air in ventilation systems for air-conditioning consumes a considerable amount of energy and affects the indoor air quality (IAQ). In this study, energy impact on ventilation systems was examined against certain IAQ objectives for indoor formaldehyde exposure risk in air-conditioned offices of Hong Kong. Thermal energy consumptions for ventilation systems and indoor formaldehyde exposure concentrations based on some regional surveys of typical offices in Hong Kong were reviewed. The thermal energy consumptions of ventilation systems operating for CO 2 exposure concentrations between 800 ppmv and 1200 ppmv for typical office buildings and the corresponding formaldehyde exposure risks were evaluated. The results showed that, for a reference indoor environment at a CO 2 exposure concentration of 1000 ppmv, the average thermal energy saving of ventilation system for a unit increment of the acceptable formaldehyde exposure limit of 1 h (loss of life expectancy of 0.0417 day) was 280 MJ m −2 yr −1; and for a unit decrement of the exposure limit of 1 h, an additional average thermal energy consumption of 480 MJ m −2 yr −1 was expected. This study would be a useful source of reference in evaluation of the energy performance of ventilation strategies in air-conditioned offices at a quantified exposure risk of formaldehyde.

인천지역 일부 학교의 실내 및 대기 중 포름알데히드 농도 평가

This study evaluated formaldehyde concentration in classrooms and on roofs at 4 elementary schools, 3 middle schools and 3 high schools in Incheon City. These schools were chosen based on their surrounding environments that included industrial site, landfill, railway, 8-lane road and harbor. Indoor concentration ranged between 4.65 and <TEX>$56.25{\mu}g/m^3$</TEX>, while that of outdoor concentration was <TEX>$1.23{\sim}10.22{\mu}g/m^3$</TEX>, both of which were below <TEX>$100{\mu}g/m^3$</TEX>, a formaldehyde criterion stipulated by the School Health Act. Indoor concentration was higher than outdoor concentration by <TEX>$1.4{\sim}5.9$</TEX> times, and there was a positive correlation between indoor and outdoor formaldehyde concentrations (R=0.49). As for indoor concentration, multi-use practice rooms had an average 2.8 times higher than that of usual classrooms with a statistically significant difference (p<0.01). Indoor formaldehyde concentration had a positive correlation with the construction year (R=0.55). The school close to the industrial complex had the highest ambient formaldehyde concentration, followed by the one near a landfill. The formaldehyde concentration in school in the vicinity of the industrial complex was twice or more than that of the school located other site. In conclusion, this study suggests that it is crucial to consider surrounding environments in selecting school sites, as it can influence ambient air contamination, as well as using construction material that emit less formaldehyde, in order to protect the health of students, teachers and school staff.

Recognizing indoor formaldehyde in binary gas mixtures with a micro gas sensor array and a neural network

Low-concentration formaldehyde (HCHO) together with ethanol/toluene/acetone/α-pinene (as an interference gas of HCHO) is detected with a micro gas sensor array, composed of eight tin oxide (SnO2) thin film gas sensors with Au, Cu, Pt or Pd metal catalysts. The characteristics of the multi-dimensional signals from the eight sensors are evaluated. A multilayer neural network with an error backpropagation (BP) learning algorithm, plus the principal component analysis (PCA) technique, is implemented to recognize these indoor volatile organic compounds (VOC). The results show that the micro gas sensor array, plus the multilayer neural network, is very effective in recognizing 0.06 ppm HCHO in single gas component and in binary gas mixtures, toluene/ethanol/α-pinene with small relative error.

Evaluation of a Passive Air Sampler for Measuring Indoor Formaldehyde

A passive air sampler, using 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, was evaluated for the determination of formaldehyde in indoor environments. Chromatography paper cleaned using a 3% hydrogen peroxide solution was experimentally determined as being the optimum absorption filter for the collection of formaldehyde (0.05 microg cm(-2) formaldehyde). From a linear-regression analysis between the mass of formaldehyde time-collected on a passive air sampler and the formaldehyde concentration measured by an active sampler, the sampling rate of the passive air sampler was 1.52 L h(-1). The sampling rate, determined for the passive air sampler in relation to the temperature (19 - 28 degrees C) and the relative humidity (30 - 90%), were 1.56 +/- 0.04 and 1.58 +/- 0.07 L h(-1), respectively. The relationship between the sampling rate and the air velocity was a linear-regression within the observed range. In the case of exposed samplers, the stability of the collected formaldehyde decreased with increasing storage time (decrease of ca. 25% after 22 days); but with the unexposed samplers the stability of the blank remained relatively unchanged for 7 days (decrease of ca. 37% after 22 days). The detection limits for the passive air sampler with an exposure time of 1 day and 7 days were 10.4 and 1.48 microg m(-3), respectively.

실내 포름알데히드 농도에 미치는 식물의 영향

Formaldehyde is a typical indoor air pollutant that has numerous adverse health problems in modern living conditions. Phytoremediation that use plants to remove contaminants from polluted media can be applied to improve indoor air quality. Two sets of experiments; 1) two rooms in newly built auditorium and 2) a bed room in 2-year-old apartment; were performed to investigate plant effects on indoor formaldehyde concentration. It was observed from the experiments that plant can help decontaminating formaldehyde at low concentration level (0.1 ppm) but the effects decreased considerably at hish concentration (1ppm). The purification effects of indoor plant also showed the periodic pattern due to its physiological activity. More purification was observed as increasing plant density in the bed room but the formaldehyde concentration returned the original concentration level in two days after removing plants. It was suggested from the results that air purification using plants is an effective means of reduction on indoor formaldehyde level, though, reduction of source is highly desirable when the concentration level is high. The results also suggest that introducing supplementary purifying aids and/or efficient ventilation could be considered due to periodic removal pattern of plant.

Personal Exposure of Children to Formaldehyde in Perth, Western Australia

P-445 Abstract: Exposure to formaldehyde has been shown to result in adverse health impacts. Children are particularly vulnerable to the respiratory impacts of formaldehyde, with some research indicating that exposure in children can exacerbate respiratory symptoms and specifically asthma. As formaldehyde levels tend to be elevated indoors, previous health studies of formaldehyde exposure have relied on stationary indoor measures as a surrogate of personal exposure. Due to the large number of potential sources of formaldehyde, this method falls short of identifying the full range of potential microenvironments in which peak formaldehyde levels may be experienced. There is also still debate about the contribution and significance of different microenvironments to personal exposure. To investigate the relationship between formaldehyde indoor, outdoor and personal exposure in children, we recruited 50 children (aged between 8 and 12) in two areas of Perth Western Australia. This cross sectional study of personal exposure aims to identify the relationship between formaldehyde concentrations and proportion of time spent indoors and outdoors as well as determining the importance of activities, lifestyle and microenvironments to exposure. Children were recruited via information sent out by interested primary schools. Each child in the study was asked to wear a passive sampler over a 24 hour period, with microenvironmental passive samplers located indoors at home, outdoors at home and indoors at school for the corresponding period. Parents were asked to assist their children in completing a questionnaire about lifestyle and behaviour and a diary for the days on which the samplers were worn. The passive samplers used filter papers impregnated with 2,4-dinitrophenylhadrazine (DNPH) exposed through a membrane with a known airflow rate. Formaldehyde was detected using high pressure liquid chromatography (HPLC), as per the standard US EPA methodology. The results of the summer sampling period for twenty five children show a wide range of personal exposure with outdoor concentrations being significantly lower than both the indoor and classroom samples.Table 1This preliminary data indicates that personal exposure concentrations are not directly correlated with either indoor, outdoor or classroom air as observed in other studies and that different microenvironments may play a role. In this preliminary assessment, no other variables explain the results observed.