Background: Agriculture is the most hazardous occupational industry for young adults. Young adults are engaging in agricultural work and interacting with common hazards, however, it is unknown how young adults are engaging with such hazards and whether administrative controls including workplace organizational factors and social influences in the workplace are associated with safe working practice. Methods: Workplace practices were examined among young adult agricultural workers (18-24). Workers responded to statements regarding their participation in six agricultural work areas, specific behaviors within each work area, risk-taking behaviors of parents, peers, and supervisors, and items about workplace organizational characteristics. A second study, conducted among swine facility workers in the Midwest, tested the effectiveness of an intervention that coupled behavioral theory with technology to increase the use of hearing protection in swine facilities. Results: Results from the cross-sectional, online survey indicated supervisor influence was more strongly associated with reported workplace behaviors than co-worker/peer or parent influence. Furthermore, organizational factors including number of hours worked each week and the presence of safety and health policies was associated with workplace behaviors Results from the intervention study suggest behavioral tracking is effective at increasing the use of hearing protection among young adult swine facility workers in the short term, however, changes in behavior are not maintained over time. Supplying hearing protection is a more effective tool in facilitating sustainable behavioral change. Conclusions: Results suggest interventions that address social and organizational factors of work to improve workplace behaviors among young adult agricultural workers should be tested.

Occupational exposure limits are generally decreasing and traditional samplers used for quantifying occupational exposures have numerous limitations: cost, disposability, detection of low concentrations, and some even fail to match international inhalable sampling conventions. A low cost, high-flow (10 L min-1) inhalable prototype sampler was developed from the 37-mm cassette and tested in previous studies. These studies called for additional field testing as an area and personal sampler. The sampler was paired with the IOM (2 L min-1), a traditional inhalable air sampler, and deployed in metal working facilities. The samplers were compared to determine whether the prototype matched the IOM and whether the new sampler could improve the sensitivity for detecting lower concentrations of metals. The following processes were sampled: welding, grinding, soldering, pouring, sawing, tending and shooting guns. A total of 21 out of 28 paired samples had detectable metals out of 15 possible metals. There were seven out of eight personal samples and 14 out of 20 area samples with detectable metal concentrations. The average sample time was seven hours, but ranged from 4.2 – 8.3 hours. The most common metals that were detected on 10 or more samples were iron, manganese, zinc, copper, and lead. Metal concentrations collected by the two samplers were not statistically different for the aggregate metal concentrations collected (p = 0.67), metals collected by sample type, personal or area (p = 0.52) or by particle “sizes,” small or large (p = 0.40), collected from the processes. While the samplers were not statistically different, linear regression equations to assess the sampler relationships showed that there were significant differences between the two samplers. Over the total metal concentrations collected, the prototype collected about 71% of what the IOM collected. By sample type, the prototype performed better during area sampling as opposed to personal sampling and by particle size, the prototype performed better in the collection of smaller, heat generated particles, as opposed to larger, mechanically generated particles. Though minor differences were found between concentrations detected on the prototype and IOM, it was determined that in general, these differences were negligible in their interpretation and comparison to occupational exposure limits. Plots also indicated that the prototype sampler performs well at sampling low concentrations of metals, however, only a small amount of metals were detected on the prototype that were not found on the IOM, therefore, the improvement of sensitivity was not assessed. High-flow sampling was hindered by the ability of air sampling pumps to maintain the required operation flow rate of 10 L min-1 for the duration of a work shift. Additional field studies are needed to determine whether the sensitivity for detecting lower concentrations of metals can be improved.

This research focuses on the evaluation of temporal and spatial variability associated with radon airborne measurements and the predictive utility of surrogate measures to estimate radon concentrations within the same environment as well as in other environments. This dissertation consists of three components. In Chapter II, "Evaluation of agreement of time-integrated basement residential radon measurements and correctness of further radon testing indicators", we investigated the temporal variability between short-term and annual residential radon measurements collected on the lowest livable level and identified housing/occupant factors that influenced each measurement as well as their differences. The false negative rate of how often the short-term test incorrectly indicated that further radon testing was unnecessary based on an annual measurement was 12 percent at the action level of 148 Bq m-3, but dropped to two percent at a 74 Bq m-3 reference level. The foundation wall material of the basement was the only significant factor to have an impact on the absolute difference between both measurements. This study has the potential to significantly influence public health policy concerning radon testing protocols, specifically the need to re-assess the EPA's current radon mitigation guidance level of 148 Bq m-3. In Chapter III, "Temporal and spatial variation associated with residential airborne radon measurements", we investigated the temporal and spatial variability between basement winter short-term and annual radon measurements performed in upper floors (i.e., non-basement) of the home and identified housing/occupant factors that influenced each measurement as well as their differences. This study found that individuals would be falsely overestimating their potential exposure to radon half the time at the EPA's action level of 148 Bq m-3 based on basement short-term tests and much more frequently (80 percent of the time) at a lower reference level of 74 Bq m-3. The presence of a sump was the only factor that was significantly associated with the absolute difference between both these measurements. This study has the potential to influence public health policy in regard to exposure surrogate measures, specifically to encourage testing of radon in living areas of the home and not relying solely on a screening measurement to estimate the concentration of radon in the entire home. In Chapter IV, "Comparative survey of outdoor, residential, and workplace radon concentrations", we investigated occupational radon concentrations in above ground workplaces in Missouri and compared them to above ground radon concentrations in nearby homes and outdoor locations and evaluated the utility of above ground annual home and outdoor concentrations to predict above ground radon concentrations at a nearby workplace. Employees at county agencies, schools, and businesses were recruited to participate in the study. Annual above ground workplace radon concentrations were found to be similar to annual radon concentrations in the upper floor of homes. Annual non-basement first floor home and outdoor radon concentrations were poor predictors of annual above ground radon concentrations at a nearby workplace. This study provides insights into the potential for above-ground radon exposures in the workplace and the potential agreement between workplace and residential radon concentrations.

No description available.

In previous studies truncated models were found to underestimate the air's upward velocity when compared to wind tunnel velocity studies, which may affect particle aspiration estimates. This work compared aspiration efficiencies using three torso geometries: 1) a simplified truncated cylinder; 2) a non-truncated cylinder; and 3) an anthropometrically realistic humanoid body. The primary aim of this work was to (1) quantify the errors introduced by using a simplified geometry and (2) determine the required level of detail to adequately represent a human form in CFD studies of aspiration efficiency. Fluid simulations used the standard k-epsilon turbulence models, with freestream velocities at 0.2 and 0.4 m s-1 and breathing velocities at 1.81 and 12.11 m s-1 to represent at-rest and heavy breathing rates, respectively. Laminar particle trajectory simulations were used to determine the upstream area where particles would be inhaled. These areas were used to compute aspiration efficiencies for facing the wind. Significant differences were found in vertical velocity and location of the critical area between the three models. However, differences in aspiration efficiencies between the three forms was less than 6% over all particle sizes, indicating that there is little difference in aspiration efficiency between torso models.

The research presented in this doctoral dissertation aimed to improve knowledge on methods to evaluate exposures to carbon-containing nanomaterials and to develop optimized respiratory filters properties to protect workers from these exposures while minimizing discomfort due to breathing resistance. In the initial study, a novel laboratory-based system generated aerosols of four carbon-containing powders (carbon black, a small-diameter (< 8 nm) multi-walled carbon nanotube (MWCNT), a large-diameter (50-80 nm) MWCNT, and a nickel-coated MWCNT) to evaluate the effectiveness of NIOSH Method 5040 for measuring masses as low as 1 μg. A targeted mass of a powder ranging from 1 to 30 μg was deposited on filters for gravimetric and elemental carbon (EC) analysis. The gravimetric mass was compared to the EC mass, and a regression model developed for each powder type. Additionally, the limit of detection (LOD) of the NIOSH Method 5040 for each powder type was determined. The regression models had significant slopes relative to zero for all powder types with all but carbon black demonstrating a statistical difference between the two methods. The LOD of NIOSH Method 5040 ranged from 4.5 for small-diameter MWCNTs to 31.8 μg for nickel-coated MWCNTs. Assuming a sample flow rate of 4.2 L/min and an 8-hour sample duration, the concentration-based LOD for NIOSH Method 5040 ranged from 2.2 μg/m3 for small-diameter MWCNTs to 15.8 μg/m3 for nickel-coated MWCNTs. These results indicate the analysis of EC is affected by the structure and elemental content of the CNTs. Additionally, based on the LOD determined for each powder type, the method may not be sufficient to assess exposures at and below the recommended exposure limit accurately without sampling durations longer than 8 hours. A second study used a laboratory-based system to evaluate an aethalometer response to carbon-containing nanomaterials including carbon black and MWCNTs. Concentrations ranging from 1 to 20 μg/m3 were generated to evaluate the device at concentrations expected in occupational settings. The concentration of the aerosol was measured by an aethalometer alongside a sample collected for EC analysis using NIOSH Method 5040. Additionally, NIOSH Method 7300 was used to determine the concentration of nickel during trials with a nickel-coated MWCNT to determine if the method along with the aethalometer can be used to assess metal-coated MWCNTs. A regression model was developed for each powder type, and the slopes for each were significant relative to zero. The LOD of the aethalometer ranged from 0.56 μg/m3 for nickel-coated MWCNTs to 7.2 μg/m3 for small-diameter MWCNTs. These results indicate the response of the aethalometer may be affected by particle structure and elemental content. NIOSH Method 5040 performed better than the aethalometer for all powder types except the nickel-coated MWCNT. Additionally, based on the LOD determined for each powder, an aethalometer may not be able to assess low-level exposures. In the third study, a mathematical model was used to predict the particle penetration and pressure drop of respirator filters with varying filter thickness, fiber diameter, solidity, and electrostatic charge. Particle penetration was determined experimentally for two different commercially available respirator filters against a sodium chloride aerosol using a scanning mobility particle sizer (SMPS). Optimized filter designs were developed using the model to minimize the pressure drop by adjusting the filter depth, fiber diameter, and solidity of the filter. The model and experimental data were used to maintain a 5% maximum penetration against nanoparticle exposures while minimizing breathing resistance. Model results indicated electrostatic charging played a significant role in improving collection efficiency of respirator filters while not increasing the breathing resistance of the filter. Filter thickness and solidity also played a key role in minimizing breathing resistance. Pressure drop decreased with decreasing solidity, however, the filter depth increased to maintain the collection efficiency of the filter. This increase in filter depth introduced a decision point of determining the practical implications of increased filter thickness on the end user. Filter depth increases dramatically as the solidity decreases below 0.20. The breathing resistance that corresponds to this design is heavily dependent on the face velocity and electrostatic charge of the filter. The electrostatic charge should be maximized during filter production as this was the dominant collection method for nanoparticle aerosols.

Occupational and environmental epidemiological studies often involve ordinal data, including antibody titer data, indicators of health perceptions, and certain psychometrics. Ideally, such data should be analyzed using approaches that exploit the ordinal nature of the scale, while making a minimum of assumptions. In this work, we first review and illustrate the analytical technique of ordinal logistic regression called the "proportional odds model". This model, which is based on a constrained ordinal model, is considered the most popular ordinal model. We use hypothetical data to illustrate a situation where the proportional odds model holds exactly, and we demonstrate through derivations and simulations how using this model has better statistical power than simple logistic regression. The section concludes with an example illustrating the use of the model in avian and swine influenza research. In the middle section of this work, we show how the proportional model assumption can be relaxed to a less restrictive model called the "trend odds model". We demonstrate how this model is related to latent logistic, normal, and exponential distributions. In particular, scale changes in these potential latent distributions are found to be consistent with the trend odds assumption, with the logistic and exponential distributions having odds that increase in a linear or nearly linear fashion. Actual data of antibody titer against avian and swine influenza among occupationally- exposed participants and non-exposed controls illustrate the fit and interpretation of the proportional odds model and the trend odds model. Finally, we show how to perform a multivariable analysis in which some of the variables meet the proportional model assumption and some meet the trend odds assumption. Likert-scaled data pertaining to violence among middle school students illustrate the fit and interpretation of the multivariable proportional-trend odds model. In conclusion, the proportional odds model provides superior power compared to models that employ arbitrary dichotomization of ordinal data. In addition, the added complexity of the trend odds model provides improved power over the proportional odds model when there are moderate to severe departures from proportionality. The increase in power is of great public health relevance in a time of increasingly scarce resources for occupational and environmental health research. The trend odds model indicates and tests the presence of a trend in odds, providing a new dimension to risk factors and disease etiology analyses. In addition to applications demonstrated in this work, other research areas in occupational and environmental health can benefit from the use of these methods. For example, worker fatigue is often self-reported using ordinal scales, and traumatic brain injury recovery is measured using recovery scores such as the Glasgow Outcome Scale (GOS).

Objectives: 1 To correlate carbon nanotube (CNT) concentrations measured by Method 5040 relative to particle count concentrations; 2 to correlate CNT concentrations measured by Method 5040 relative to black carbon concentrations measured with an aethalometer; 3 to compare elemental carbon (EC) concentrations measured by Method 5040 among various CNT types and purities. Methods: CNT samples were collected using 25 mm quartz fiber filters and analyzed for EC by Method 5040. An aethalometer was simultaneously used to measure black carbon concentrations. Samples sent for EC analysis included various CNT types (multi-walled, single-walled) and purities (high, low). Levels of EC concentration were subjected to a two-way analysis of variance having two levels of CNT type and two levels of purity. Results: No correlation was established between CNT count and EC concentration, but a correlation was found between CNT volumetric and total carbon (TC) concentration. A significant correlation between black carbon and TC concentration was found. Method 5040 was found to have a positive bias for TC, and the aethalometer was found to have a positive bias for black carbon. Lastly, this study found that CNT type had no effect on EC concentration, but purity did have a significant effect on EC concentration. Conclusions: Samples analyzed by Method 5040 were found to have 6 - 19% EC content, and thus surprisingly high amounts of organic carbon. It is reasoned that significant amounts of impurities were introduced to CNT samples while travelling through the experimental apparatus. When TC concentrations were plotted against black carbon concentrations a significant relationship was found and the bias of Method 5040 and the aethalometer cancelled out. Future research is needed to investigate the aethalometer as a surrogate for Method 5040. Until then, those conducting CNT exposure assessments should use a 25 mm cassette and increase the volume sampled to achieve a reporting limit lower than the NIOSH recommended CNT REL of 7 µg/m3.

Semi-volatile lower chlorinated PCBs (LC-PCBs), comprised of mostly tetra or lower chlorinated congeners, are detected in old buildings and outdoors in high concentrations. PCBs cause endocrine disruption, neurotoxicity and many other adverse effects, and are human carcinogens. Epidemiological studies so far have relied upon serum concentrations of PCBs or OH-PCBs as markers of exposure. Despite the detection of LC-PCBs in high levels in buildings and other environments, only a few studies have reported LC-PCBs in human serum. One of the reasons for low serum detection of LC-PCBs could be the further biotransformation and excretion of OH-PCBs from the body. Therefore, the objective of this dissertation research was to study the metabolism of one of the LC-PCBs in rats and to identify a suitable metabolite marker of inhalation exposure for a future epidemiological study in humans. We chose PCB3 (4-chlorobiphenyl), a mono chlorinated PCB found in high concentrations in many buildings, as a model to study the metabolism. The first aim was to identify final metabolites of PCB3 in vivo. Male Sprague-Dawley rats were held in metabolism cages following exposure to PCB3 via i.p. injection. Blood, urine and feces were collected, and an analytical method for extraction of PCB3 metabolites was developed. By identifying the metabolites by LC/MS, a complete biotransformation pathway for PCB3 was elucidated. Major urinary metabolites of PCB3 were sulfates and mercapturates, while glucuronides and free phenolic forms were minor. The second aim was to study the disposition and toxicity of phenolic and sulfate metabolites after inhalation exposure to PCB3 in female Sprague-Dawley rats. Airborne PCB3 vapor was generated in a flask and passed through an inhalation exposure system, where rats were exposed via nose-only inhalation. Both hydroxylated and sulfated metabolites were detected in serum, liver, lungs, and brain. The serum clearance half-lives of these metabolites were less than two hours. Serum chemistry parameters were similar in PCB3 exposed and control rats. As a marker of bioactivation of PCB3 to electrophilic species, 8-oxo-dG was quantified in urine, but the difference was not statistically significant between control and exposed rats. The third aim was to study the routes of excretion of metabolites after inhalation to airborne PCB3. Bile cannulated and intact rats were exposed to PCB3 via nose only inhalation. Metabolites detected in bile were mostly sulfates and some glucuronide. Fecal metabolites were exclusively phenols despite very low concentration of free phenolic forms in bile. Peak excretion of metabolites in feces and urine occurred within 24 h, and over sixty percent of the dose was recovered within 24 h. The major route of excretion of PCB3 was urine in the form of sulfated metabolites. Sulfated metabolites were stable in urine for a month without aid of any preservatives. This dissertation shows that PCB3 is rapidly metabolized to phenols and conjugated mostly to sulfates. Conjugated metabolites, elaborated into bile, are either reabsorbed or hydrolyzed in the gut and excreted in feces as phenolic forms. Serum concentrations of sulfates are higher than free phenolic forms at any time after exposure, and are also detected in lungs and brain. PCB3 sulfates are stable metabolites and can serve as a metabolite marker of inhalation exposure to PCB3.

Confined farm animals generate large amounts of excrement on-site. Many toxic substances emitted from Concentrated Animal Feeding Operations (CAFOs) emanate from that manure including hydrogen sulfide. There is growing concern that these pollutants, including hydrogen sulfide, may lead to adverse health effects among people living close to these operations. Iowa law mandates that separation distances be established from CAFOs to residences, public areas, and public buildings to protect human health. The primary objective of this study was to assess the adequacy of current separation distance requirements established in Iowa to protect for the Health Effects Standard (HES) and Health Effects Value (HEV) of hydrogen sulfide concentrations emanating from swine CAFOs in Iowa. Specifically, the research examined: 1) the characteristics of swine weight dense areas, 2) if current CAFO setback distance regulations in Iowa protect for the HES and HEV of hydrogen sulfide nearest the largest swine weight CAFO, and 3) if current CAFO setback distance regulations in Iowa protect for the HES and HEV of hydrogen sulfide for an area of Iowa which has the greatest swine weight density. The results suggest that the highest swine weight dense areas generally have a greater median and average swine weight per CAFO than is observed for all active swine CAFOs in Iowa. The high swine weight areas are also generally influenced greatly by a few very large swine CAFOs. Additionally, these areas tend to have a high CAFO density but are not located in the highest CAFO dense areas of Iowa. The HEV level of hydrogen sulfide is estimated to be exceeded in a total area of 423,568 m2 beyond the associated separated distance for the largest active swine CAFO alone in 2004. This indicates that the 914.4 m (3,000 ft) separation distance does not protect against the HEV of hydrogen sulfide for the largest swine CAFO in Iowa. The HES of hydrogen sulfide was not exceeded in this area. Additionally, the estimated concentrations of hydrogen sulfide in the highest swine weight dense area did not exceed the HES or HEV beyond the minimum separation distances.