Di-2-ethylhexyl Phthalate Emission Research Articles

Impact of mold growth on di(2-ethylhexyl) phthalate emission from moist wallpaper

Flood damage can increase indoor concentrations of di(2-ethylhexyl) phthalate (DEHP) and molds in households with wallpaper. Wallpaper water content can affect its DEHP emission into indoor environments; however, the influence of mold growth on this DEHP emission remains unclear. Here, we evaluated whether mold growth affects DEHP emission from moist wallpaper (moist WP). Experiments were conducted in glass chambers with wallpaper containing 12.7% (w/w) DEHP and a dust tray sample system at approximately 28 °C and 100% relative humidity (RH). The experimental groups were (1) moist WP, (2) moist WP + Aspergillus versicolor (AV), (3) moist WP + Cladosporium cladosporioides, (4) moist WP + Penicillium chrysogenum, and (5) moist WP + mold mixture. Mold growth on the wallpaper and DEHP emission into air and onto dust were analyzed at nine time-points over 30 days. Initially, the moist WP group emitted relatively high concentrations of DEHP into air, but after at least 8 days, the concentration of DEHP emitted by the mold-added groups exceeded that of the moist WP group. DEHP emission onto dust, especially from the moist WP group, increased considerably at day 15. During the experimental period, the moist WP (13.63 ± 4.67 μg) and moist WP + AV (13.93 ± 0.49 μg) groups emitted higher cumulative amounts of DEHP onto dust. During the 30-day experimental period, obvious mold growth occurred over days 15–30. Moreover, the moist WP group exhibited relatively higher and lower cumulative DEHP emission into air than the mold-added groups during days 2–10 (2.71 vs. 1.94–2.94 μg) and 15–30 (1.16 vs. 1.61–2.12), respectively; a contrasting trend was observed for cumulative DEHP emission onto dust. In conclusion, mold growth affects DEHP emission from water-damaged wallpaper, and the removal or cleaning of wet wallpaper, particularly those with visible mold growth, is critical from a public health perspective.

A general mechanistic model for predicting the fate and transport of phthalates in indoor environments.

A mechanistic model that considers particle dynamics and their effects on surface emissions and sorptions was developed to predict the fate and transport of phthalates in indoor environments. A controlled case study was conducted in a test house to evaluate the model. The model-predicted evolving concentrations of benzyl butyl phthalate in indoor air and settled dust and on interior surfaces are in good agreement with measurements. Sensitivity analysis was performed to quantify the effects of parameter uncertainties on model predictions. The model was then applied to a typical residential environment to investigate the fate of di-2-ethylhexyl phthalate (DEHP) and the factors that affect its transport. The predicted steady-state DEHP concentrations were 0.14μg/m3 in indoor air and ranged from 80 to 46000μg/g in settled dust on various surfaces, which are generally consistent with the measurements of previous studies in homes in different countries. An increase in the mass concentration of indoor particles may significantly enhance DEHP emission and its concentrations in air and on surfaces, whereas increasing ventilation has only a limited effect in reducing DEHP in indoor air. The influence of cleaning activities on reducing DEHP concentration in indoor air and on interior surfaces was quantified, and the results showed that DEHP exposure can be reduced by frequent and effective cleaning activities and the removal of existing sources, though it may take a relatively long period of time for the levels to drop significantly. Finally, the model was adjusted to identify the relative contributions of gaseous sorption and particulate-bound deposition to the overall uptake of semi-volatile organic compounds (SVOCs) by indoor surfaces as functions of time and the octanol-air partition coefficient (Koa ) of the chemical. Overall, the model clarifies the mechanisms that govern the emission of phthalates and the subsequent interactions among air, suspended particles, settled dust, and interior surfaces. This model can be easily extended to incorporate additional indoor source materials/products, sorption surfaces, particle sources, and room spaces. It can also be modified to predict the fate and transport of other SVOCs, such as phthalate-alternative plasticizers, flame retardants, and biocides, and serves to improve our understanding of human exposure to SVOCs in indoor environments.

Higher moisture content is associated with greater emissions of DEHP from PVC wallpaper

Water damage and moisture in buildings may become more prevalent due to the increasing frequency of extreme precipitation and flooding events resulting from climate change. However, the effects of moisture levels on phthalate emissions from building materials are still underreported. This study aims to evaluate the effect of moisture content (MC) on the level of di-(2ethylhexyl) phthalate (DEHP) emitted from plastic wallpaper (0.22wt% DEHP) within 15 days in a closed chamber. A scenario of short-term exposure to DEHP in buildings suffering from water damage was simulated. Experiments, controlled at 100% relative humidity (RH) of air and 28°C, were conducted under the following three conditions: (I) without wallpaper (control chamber), (II) dry wallpaper (MC at 3.57%) and (III) damp wallpaper (MC at 52.31%). Air and dust samples were collected at the elapsed time of 2, 4, 6, 8, 10, 13 and 15 days, and the wipe sample was collected on the last day. Higher DEHP concentrations were found to be emitted into the air and adsorbed on the dust for wallpapers with higher MC%. DEHP levels in the air exhibited an increasing trend with the length of the experiment. Overall, it was found that approximately 35.31% more total DEHP mass was released into the air, dust and wipe samples from damp wallpapers compared to dry wallpapers. It is concluded that DEHP emissions from plastic materials are affected by the inner moisture percentage.

Estimating Emissions and Environmental Fate of Di-(2-ethylhexyl) Phthalate in Yangtze River Delta, China: Application of Inverse Modeling.

A georeferenced multimedia model was developed for evaluating the emissions and environmental fate of di-2-ethylhexyl phthalate (DEHP) in the Yangtze River Delta (YRD), China. Due to the lack of emission inventories, the emission rates were estimated using the observed concentrations in soil as inputs for the multimedia model solved analytically in an inverse manner. The estimated emission rates were then used to evaluate the environmental fate of DEHP with the regular multimedia modeling approach. The predicted concentrations in air, surface water, and sediment were all consistent with the ranges and spatial variations of observed data. The total emission rate of DEHP in YRD was 13.9 thousand t/year (95% confidence interval: 9.4-23.6), of which urban and rural sources accounted for 47% and 53%, respectively. Soil in rural areas and sediment stored 79% and 13% of the total mass, respectively. The air received 61% of the total emissions of DEHP but was only associated with 0.2% of the total mass due to fast degradation and intensive deposition. We suggest the use of an inverse modeling approach under a tiered risk assessment framework to assist future development and refinement of DEHP emission inventories.

A reference method for measuring emissions of SVOCs in small chambers

Semi-volatile organic compounds (SVOCs) are indoor air pollutants that may have significant adverse effects on human health. Although emissions of volatile chemicals from building materials and consumer products are usually characterized in small chambers, few chamber studies have been conducted for SVOCs due to the challenges associated with analysis and the lack of validation procedures. There is an urgent need for a reliable and accurate chamber test method to verify these measurements. A reference method employing a specially-designed chamber has been developed and is undergoing extensive evaluation. A pilot inter-laboratory study (ILS) has been conducted with six laboratories performing chamber tests under identical conditions for di-2-ethylhexyl phthalate (DEHP). Results from this study showed inter-laboratory variations of 24% for DEHP emission rates, with closer agreement observed among intra-laboratory measurements for most of the participating laboratories. A mechanistic emission model fits well to the measured concentration profiles, demonstrating the feasibility of the proposed reference method to independently assess laboratory performance and validate SVOC emission tests.

Predicting the transport process of indoor semi-volatile organic compounds via lattice Boltzmann method

In this paper, a model consisting of the lattice Boltzmann (LB) method for fluid flow and mass transport and the cellular automata probabilistic method employed for simulating the movement of airborne particles to predict the transport process of indoor semi-volatile organic compounds (SVOCs) is developed. This model is used to obtain the concentration distribution of the airborne di-2-ethylhexyl phthalate (DEHP), a typical SVOC, including the gas-phase DEHP and the particle-phase DEHP in the given indoor environment where the vinyl flooring is the only emission source. Research on the influence of airborne particles on the transport of indoor airborne DEHP is made through comparing concentration distribution of DEHP in the cases of different airborne particle mass concentration and diameter, respectively. The DEHP emission rate under different ventilation types is also studied. Simulation results show that the airborne particle concentration directly affects the indoor DEHP emission. The increase of the indoor airborne particle mass concentration or the decrease of the airborne particle diameter will both help reduce the gas phase DEHP concentration. The emission rate increases with the increase of the airborne particle concentration. The indoor DEHP pollution will be reduced when the air changes per hour (ACH) increases. In general, Comparing with the cross ventilation method, the displacement one is more beneficial to reduce indoor DEHP pollution.

Influence of suspended particles on indoor semi-volatile organic compounds emission

Semi-volatile organic compounds (SVOCs) have been attracting more and more attentions to many researchers in these years. Because SVOCs have a strong tendency for adsorption to suspended particles, we take the effect of suspended particles into account to study the transport mechanism of SVOCs in the air. We establish a mathematical model to describe the transport mechanism of SVOCs, and study the transport processes of both gas- and particle-phase di-2-ethylhexyl phthalate (DEHP) in Field and Laboratory Emission Cells (FLECs). The predictions by the proposed model not only fit well with the experimental data of previous studies, but also show that the gas-phase DEHP concentration increases rapidly in the first few seconds and increases slowly during the following 200 days due to different transport mechanisms in the two periods. Meanwhile, when the particle radiuses are of the order of micron and the air changes per hour (ACH) is large enough, the characteristic time for DEHP getting gas/particle equilibrium is much longer than the residence time of a particle in the flow field, and thus there is no significant influence of suspended particles on the total concentration of DEHP in the air. Oppositely, the influence of particles on DEHP emission will be enhanced for a cycling air flow system with a small ACH, where increasing ACH will reduce the concentrations of particle-phase SVOCs. Besides, if the particle radiuses are of the order of nanometer, decreasing the particle radiuses will shorter the characteristic time for DEHP getting gas/particle equilibrium, and finally increase the particle-phase concentration of DEHP.

Predicting Residential Exposure to Phthalate Plasticizer Emitted from Vinyl Flooring: A Mechanistic Analysis

A two-room model is developed to estimate the emission rate of di-2-ethylhexyl phthalate (DEHP) from vinyl flooring and the evolving gas-phase and adsorbed surface concentrations in a realistic indoor environment. Because the DEHP emission rate measured in a test chamber may be quite different from the emission rate from the same material in the indoor environment the model provides a convenient means to predict emissions and transport in a more realistic setting. Adsorption isotherms for phthalates and plasticizers on interior surfaces, such as carpet, wood, dust, and human skin, are derived from previous field and laboratory studies. Log-linear relationships between equilibrium parameters and chemical vapor pressure are obtained. The predicted indoor air DEHP concentration at steady state is 0.15 microg/m3. Room 1 reaches steady state within about one year, while the adjacent room reaches steady state about three months later. Ventilation rate has a strong influence on DEHP emission rate while total suspended particle concentration has a substantial impact on gas-phase concentration. Exposure to DEHP via inhalation, dermal absorption, and oral ingestion of dust is evaluated. The model clarifies the mechanisms that govern the release of DEHP from vinyl flooring and the subsequent interactions with interior surfaces, airborne particles, dust, and human skin. Although further model development, parameter identification, and model validation are needed, our preliminary model provides a mechanistic framework that elucidates exposure pathways for phthalate plasticizers, and can most likely be adapted to predict emissions and transport of other semivolatile organic compounds, such as brominated flame retardants and biocides, in a residential environment.

Predicting Emissions of SVOCs from Polymeric Materials and Their Interaction with Airborne Particles

A model that predicts the emission rate of volatile organic compounds (VOCs) from building materials is extended and used to predict the emission rate of semivolatile organic compounds (SVOCs) from polymeric materials. Reasonable agreement between model predictions and gas-phase di-2-ethylhexyl phthalate (DEHP) concentrations is achieved using data collected in a previous experimental study that measured emissions of DEHP from vinyl flooring in two very different chambers. While emissions of highly volatile VOCs are subject to "internal" control (the material-phase diffusion coefficient), emissions of the very low volatility SVOCs are subject to "external" control (partitioning into the gas phase, the convective mass-transfer coefficient, and adsorption onto interior surfaces). The effect of SVOCs partitioning onto airborne particles is also examined. The DEHP emission rate is increased when the gas-phase concentration is high, and especially when partitioning to the airborne particles is strong. Airborne particles may play an important role in inhalation exposure as well as in transporting SVOCs well beyond the source. Although more rigorous validation is needed, the model should help elucidate the mechanisms governing emissions of phthalate plasticizers, brominated flame retardants, biocides, and other SVOCs from a wide range of building materials and consumer products.

Diethylhexylphthalate as an environmental contaminant — A review

Di(2-ethylhexyl)phthalate (DEHP) is a priority pollutant in several countries; annual production amounts to 3–4 million tonnes. Approximately 95% is used as a plasticizer in polyvinylchloride (PVC). DEHP is emitted to the environment during the production of plastics and plastic products, during their use and after disposal. In the environment, physico-chemical degradation of DEHP is practically non-existent. Biodegradation occurs readily under aerobic conditions ( t 1 2 = 2–4 weeks ), but not under anaerobic conditions. The acute toxicity of DEHP to mammals is low. Many subchronic and chronic effects have, however, been identified. The most important of these are: influence on the liver and energy metabolism, teratogenicity, adverse effects on male reproductive organs, carcinogenicity and influence on the immune system. On the basis of figures concerning human exposure, most of these effects are not likely to occur. With respect to carcinogenicity the situation is uncertain, especially for some risk groups. The ecotoxicology of DEHP is especially relevant for aquatic communities where data are contradictory: several authors have found adverse effects on Daphnia and fish species after exposure to the present environmental concentrations; others, however, produced less alarming results. Emissions of DEHP can be reduced by the biological treatment of wastewater and waste gas, the use of alternative plasticizers in PVC or the substitution of other plastics for PVC.