Characterization of Inhalation Exposure to Engineered Nanomaterials in Consumer Spray Products

Abstract

the relative biass in particle number and surface area were constant over time under ventilated conditions. The ConsExpo Nano as a nano-specific model had stable estimates of short-term exposure (within 30 min) with less than 50 % relative biases in all metrics. The deposition models showed similar estimates of the number and mass of deposited nanoparticles in each respiratory region for monodispersed particles. The estimates of deposited particles in the polydispersed size range were also similar among the deposition models, particularly for the nanoparticle range in the head airway and alveolar region. In conclusions, it was found that the particle size can be changed to inhalable forms during spraying process compared to initial size distribution in suspensions, but still most of particles in the air after spraying are nano-sized. Propellant sprays released a larger quantity of nanoparticles which dispersed over a greater distance and persisted for a longer time in the air due to their small size, thereby the propellant sprays can cause a higher risk of exposure for consumers. Much higher number of nanoparticles could be deposited in alveolar region during propellant use in near distance. Inhalation exposure models used in this study were only suitable for estimating the short-term exposure within half an hour, but they are not suitable for long-term exposure more than hours. For nanoparticle range, deposition models can provide the stable estimates of deposited dose except for tracheobronchial region.

Yeh-Schum 5-Lobe model and stochastic lung model) models with assumptions of monodispersed and polydispersed particle sizes. The modeled estimates of the inhaled doses by the consumer exposure models were suitable for short-term (10 min) by exposure scenarios, and the relative bias was 3-50% in each model, whereas the estimates for long-term exposure (more than hours) significant deviated from the experimental estimates in the unventilated condition. The relative biases between the modeled and the experimental were relatively stable for short-term exposure

2, 3 m, far-field) by distance from the spraying location. Inhalation exposure including inhaled dose at breathing zone and deposited dose in respiratory regions were estimated using the experimental data. Nanoparticles released from the propellant sprays persisted for long time more than two hours in the air and dispersed over a far distance due to their small size (1,466-5,565 particles/cm3). The pump sprays produced larger droplets that settled out of the air relatively close to the source, so the concentration was similar to background level (< 200 particles/cm3). The estimates of inhalation exposure also suggested that exposure to nanoparticles was greater with propellant sprays (1.2×108±4.0×107 particles/kgbw/day) than pump sprays (2.7×107±6.5×106 particles/kgbw/day). It was found that much higher number of nanoparticles could be deposited in alveolar region which is a deeper part of respiratory tract during propellant use in near distance (4.6×107±1.6×107 particles/kgbw/day), but they relatively influenced a little than large particles in terms of particle mass. Large particles more than micrometer released from pump sprays did not influence the inhalation exposure due to their heavier mass that can be settled to bottom after spraying. Lastly, Exposure models including European Center for Ecotoxicology of Chemicals Targeted Risk Assessment (ECETOC TRA), Consumer Exposure Model (CEM), SprayExpo, ConsExpo and ConExpo Nano were used to estimate the inhaled dose in various exposure scenarios considering the use conditions. A relative bias between modeled and experimental estimates was used for comparison. A relative bias between modeled and experimental estimates was used for comparison. The deposited dose in respiratory regions was estimated using International Commission on Radiological Protection (ICRP) model and multiplepath particle dosimetry (MPPD

Engineered nanomaterials (ENMs) have been used in a number of consumer products and the nanotechnology-based products are increasing in the market. With the rapid increase in use of products containing ENMs, there has also been a significant concern raised about their environmental safety, especially with regards to the potential toxicity to humans and the environment. The objectives of this study were: to characterize the physicochemical properties between ENM suspensions and aerosols released after spraying

to characterize the spatialtemporal dispersion of airborne ENMs during the use of spray products and to estimate inhalation exposure

to estimate the inhalation exposure to aerosols released from the consumer spray products using exposure models and to compare the deposited doses in each part of respiratory regions using deposition models. First, a total of eleven consumer spray products were selected to characterize the physicochemical properties in suspended ENMs in product solutions and particles released after spraying in the air. A dynamic light scattering (DLS), transmission electron microscopy (TEM) and inductively coupled plasma-mass spectrometer (ICP-MS) were used to obtain the information on the particle size, morphology, coagulated state, and chemical compositions for suspensions in each product. Direct-reading instruments (DRIs), TEM and ICP-MS were used to characterize the aerosolized ENMs by distance from the spraying location in a glove-box chamber. The median diameter (D50) of suspension in solutions measured by DLS showed a wide range from 215 to 347 nm, while individual particle sizes were confirmed from 2.9 to 47.5 nm for all products by TEM. Various metallic elements including labelled ENMs such as nanosilver were also identified by ICP-MS. The size of released individual particles was ranged from 7 to 44 nm and their aggregates were from 101 to 1,019 nm in near distance (< 1 m). The particles released from the propellant sprays were also identified in far distance (2 m), but there was no visible particle from the pump sprays by TEM. The number concentration of nanoparticles from the propellant sprays increased from 104 to 6,002 particles/cm3/g at near distance and dispersed to far distance from 121 to 5,572 particles/cm3/g, while the droplets emitted from pump sprays did not influence particle dispersion. Secondly, a total of eight spray products including five propellant and three pump types were selected to evaluate the spatial-temporal dispersion of airborne nanoparticles. DRIs to measure the particles, as well as filter sampling were used to examine physicochemical properties of aerosolized ENMs. Sampling was conducted simultaneously at each location (1 m, near-field