Inadequate Personal Protective Equipment Factors and Odds Related to Acute Pesticide Poisoning: A Meta-Analysis Report.

INTRODUCTION: Acute pesticide poisoning (APP) continues to affect farm workers, especially in low- and middle-income countries (LMIC). The dose-response relationship between exposure and APP is well-researched, but pesticide exposure assessment in a practical environment is difficult to perform, considering various work practices and protections in place. It is well known that inadequate personal protective equipment (PPE) use is a risk factor of APP. However, it is unknown which types of inadequate PPE use, such as face or other types of general protection, are most harmful. METHODS: This study aimed to identify if inadequate PPE use is an indicator of APP risk following established specifications for meta-analysis of epidemiological studies. Included studies reported an odds ratio (OR) between PPE use to APP in agricultural workers. Data extracted from selected articles included authors, publication year, country of origin, farm type, population size, method of data collection and time frame of reported symptoms, job task, type of PPE and pesticides used, adjustments made in analysis, OR for APP, and 95% confidence intervals (CI). Meta-analysis was performed using a random effects model, where ORs were pooled to assess an overall estimate for poisoning odds. RESULTS: Our findings suggested that inadequate PPE use was associated with increased odds (OR = 1.57, 95% CI = 1.16-2.12) of having APP. Failure to use general protection and inadequate face protection increased odds of APP by 1.29 times (95% CI = 0.88-1.90) and 1.92 times (95% CI = 1.23-3.00), respectively. CONCLUSIONS: The meta-analysis results indicate that improper facial protection and general protection are not differently associated with APP odds. Our study concludes that more robust protection against inhalation and dermal contact are critical because any gaps in comprehensive full-body PPE would put workers and exposed populations at APP risk.

Assessment of fine particles released during paper printing and shredding processes.

In this study, we investigated the airborne particles released during paper printing and paper shredding processes in an attempt to characterize and differentiate these particles. Particle characteristics were studied with real time instruments (RTIs) to measure concentrations and with samplers to collect particles for subsequent microscopy and cytotoxicity analysis. The particles released by paper shredding were evaluated for cytotoxicity by using in vitro human lung epithelial cell models. A substantial amount of particles were released during both the shredding and printing processes. We found that the printing process caused substantial release of particles with sizes of less than 300 nm in the form of metal granules and graphite. These released particles contained various elements including Al, Ca, Cu, Fe, Mg, N, K, P, S and Si. The particles released by the paper shredding processes were primarily nanoparticles and had a peak size between 27.4 nm and 36.5 nm. These paper particles contained elements including Al, Br Ca, Cl, Cr, Cu, Fe, Mg, N, Na, Ni P, S and Si, as determined by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) and single-particle inductively coupled plasma-mass spectroscopy (SP-ICP-MS) analysis. Although various metals were identified in the paper particles, these particles did not elicit cytotoxicity to simian virus-transformed bronchial epithelial cells (BEAS2B) and immortalized normal human bronchial epithelial cells (HBE1). However, future studies should investigate other cytotoxicity effects of these paper particles in various types of lung cells to identify potential health effects of the particles.

Sampling Techniques on Collecting Fine Carbon Nanotube Fibers for Exposure Assessment.

Carbon nanotube (CNT) sampling using an open-faced 25 mm cassette fiber sampling method and a newly developed direct sampling device was evaluated for the size fractioned analysis of collected airborne CNT fibers to improve the sampling and analytical methods. The open-faced 25 mm cassette fiber sampling method primarily collected large agglomerates, with the majority of collected particles being larger than two micrometer in size. Most of CNT structures collected by the new direct sampling device were individual fibers and clusters smaller than one micrometer with a high particle number concentration discrepancy compared to the open-faced 25 mm cassette method raising the concern of this sampling method to representatively characterize the respirable size fraction of CNT aerosols. This work demonstrates that a specialized technique is needed for collecting small fibers to provide a more representative estimate of exposure. It is recommended that an additional sampler be used to directly collect and analyze small fibers in addition to the widely accepted sampling method which utilizes an open-faced 25 mm cassette.

Particle Emissions from Laboratory Activities Involving Carbon Nanotubes.

This site study was conducted in a chemical laboratory to evaluate nanomaterial emissions from 20-30 nm diameter bundles of single-walled carbon nanotubes (CNTs) during product development activities. Direct-reading instruments were used to monitor the tasks in real time and airborne particles were collected using various methods to characterize released nanomaterials using electron microscopy and elemental carbon (EC) analyses. CNT clusters and a few high aspect ratio particles were identified as being released from some activities. The EC concentration at the source of probe sonication was found to be higher than other activities including weighing, mixing, centrifugation, coating and cutting. Various sampling methods all indicated different levels of CNTs from the activities, however, the sonication process was found to release the highest amounts of CNTs. It can be cautiously concluded that the task of probe sonication possibly released nanomaterials into the laboratory and posed a risk of surface contamination. Based on these results, the sonication of CNT suspension should be covered or conducted inside a ventilated enclosure with proper filtration or a glovebox to minimize the potential of exposure.

Identification and Mitigation of Generated Solid By-Products during Advanced Electrode Materials Processing.

A scalable, solid-state elevated-temperature process was developed to produce high-capacity carbonaceous electrode materials for energy storage devices via decomposition of a starch-based precursor in an inert atmosphere. In a separate study, it is shown that the fabricated carbonaceous architectures are useful as an excellent electrode material for lithium-ion, sodium-ion, and lithium-sulfur batteries. This article focuses on the study and analysis of the formed nanometer-sized by-products during the lab-scale synthesis of the carbon material. The material production process was studied in operando (that is, during the entire duration of heat treatment). The unknown downstream particles in the process exhaust were collected and characterized via aerosol and liquid suspensions, and they were quantified using direct-reading instruments for number and mass concentrations. The airborne emissions were collected using the Tsai diffusion sampler (TDS) for characterization and further analysis. Released by-product aerosols collected in a deionized (DI) water trap were analyzed, and the aerosols emitted from the post-water-suspension were collected and characterized. After long-term sampling, individual particles in the nanometer size range were observed in the exhaust aerosol with layer-structured aggregates formed on the sampling substrate. Upon the characterization of the released aerosol by-products, methods were identified to mitigate possible human and environmental exposures upon industrial implementation.

Toxicity mechanism in fetal lung fibroblast cells for multi-walled carbon nanotubes defined by chemical impurities and dispersibility.

Multi-walled carbon nanotubes (MWCNTs) are beneficial in a wide range of applications in fields such as electronics, optics and nano-medicine, so knowledge concerning their effect on human health is important. Physiochemical properties of MWCNTs can greatly affect their toxicity, however, there are no reports discussing the effect of size and chemical composition of MWCNTs on the toxic response of human lung cells. In this study, MWCNTs of two different purity grades were characterized and their toxic effects were compared on normal fetal lung fibroblast MRC-5 cells. The toxic effect on MRC-5 cells following 1-3 days exposure to low concentrations of research grade (RG) and industrial grade (IG) MWCNTs were studied using multiple biological assays. MWCNTs uptake in MRC-5 cells was analyzed using TEM. After physical and chemical analysis, RG-MWCNTs revealed contamination with MoS2 and were readily suspended in distilled water while IG-MWCNTs had no MoS2 contamination and much lower dispersibility. For a wide range of concentrations and exposure times, cells treated with RG-MWCNTs had distinctly reduced cell viability as compared to cells treated with IG-MWCNTs. Treatment with RG-MWCNTs resulted in high reactive oxygen/nitrogen species (ROS/RNS) levels indicating an oxidative stress mechanism while IG-MWCNT treated cells had low ROS/RNS amounts and a distorted cell membrane pointing towards a non-oxidative stress mechanism. Both agglomerates and individual MWCNTs were internalized efficiently by MRC-5 cells, which resulted in cell damage and ultimately cell death. Altogether, this study shows that the MoS2 contamination and size of MWCNTs' agglomerates affect the mechanism of toxicity in human fetal lung fibroblasts.

Assessing the first wave of epidemiological studies of nanomaterial workers.

The results of early animal studies of engineered nanomaterials (ENMs) and air pollution epidemiology suggest that it is important to assess the health of ENM workers. Initial epidemiological studies of workers' exposure to ENMs (<100 nm) are reviewed and characterized for their study designs, findings, and limitations. Of the 15 studies, 11 were cross-sectional, 4 were longitudinal (1 was both cross-sectional and longitudinal in design), and 1 was a descriptive pilot study. Generally, the studies used biologic markers as the dependent variables. All 11 cross-sectional studies showed a positive relationship between various biomarkers and ENM exposures. Three of the four longitudinal studies showed a negative relationship; the fourth showed positive findings after a 1-year follow-up. Each study considered exposure to ENMs as the independent variable. Exposure was assessed by mass concentration in 10 studies and by particle count in six studies. Six of them assessed both mass and particle concentrations. Some of the studies had limited exposure data because of inadequate exposure assessment. Generally, exposure levels were not very high in comparison to those in human inhalation chamber studies, but there were some exceptions. Most studies involved a small sample size, from 2 to 258 exposed workers. These studies represent the first wave of epidemiological studies of ENM workers. They are limited by small numbers of participants, inconsistent (and in some cases inadequate) exposure assessments, generally low exposures, and short intervals between exposure and effect. Still, these studies are a foundation for future work; they provide insight into where ENM workers are experiencing potentially adverse effects that might be related to ENM exposures.

Performance of Particulate Containment at Nanotechnology Workplaces.

The evaluation of engineering controls for the production or use of carbon nanotubes (CNTs) was investigated at two facilities. These controls assessments are necessary to evaluate the current status of control performance and to develop proper control strategies for these workplaces. The control systems evaluated in these studies included ventilated enclosures, exterior hoods, and exhaust filtration systems. Activity-based monitoring with direct-reading instruments and filter sampling for microscopy analysis were used to evaluate the effectiveness of control measures at study sites. Our study results showed that weighing CNTs inside the biological safety cabinet can have a 37% reduction on the particle concentration in the worker's breathing zone, and produce a 42% lower area concentration outside the enclosure. The ventilated enclosures used to reduce fugitive emissions from the production furnaces exhibited good containment characteristics when closed, but they failed to contain emissions effectively when opened during product removal/harvesting. The exhaust filtration systems employed for exhausting these ventilated enclosures did not provide promised collection efficiencies for removing engineered nanomaterials from furnace exhaust. The exterior hoods were found to be a challenge for controlling emissions from machining nanocomposites: the downdraft hood effectively contained and removed particles released from the manual cutting process, but using the canopy hood for powered cutting of nanocomposites created 15%-20% higher ultrafine (<500 nm) particle concentrations at the source and at the worker's breathing zone. The microscopy analysis showed that CNTs can only be found at production sources but not at the worker breathing zones during the tasks monitored.

Evaluation of environmental filtration control of engineered nanoparticles using the Harvard Versatile Engineered Nanomaterial Generation System (VENGES).

Applying engineering controls to airborne engineered nanoparticles (ENPs) is critical to prevent environmental releases and worker exposure. This study evaluated the effectiveness of two air sampling and six air cleaning fabric filters at collecting ENPs using industrially relevant flame-made engineered nanoparticles generated using a versatile engineered nanomaterial generation system (VENGES), recently designed and constructed at Harvard University. VENGES has the ability to generate metal and metal oxide exposure atmospheres while controlling important particle properties such as primary particle size, aerosol size distribution, and agglomeration state. For this study, amorphous SiO(2) ENPs with a 15.4 nm primary particle size were generated and diluted with HEPA-filtered air. The aerosol was passed through the filter samples at two different filtration face velocities (2.3 and 3.5 m/min). Particle concentrations as a function of particle size were measured upstream and downstream of the filters using a specially designed filter test system to evaluate filtration efficiency. Real time instruments (FMPS and APS) were used to measure particle concentration for diameters from 5 to 20,000 nm. Membrane-coated fabric filters were found to have enhanced nanoparticle collection efficiency by 20-46 % points compared to non-coated fabric and could provide collection efficiency above 95 %.