Risk Assessment Science


Monday, May 23, 2016, 10:30 AM - 12:30 PM


Benzene Exposures and Risk Potential for Vehicle Mechanics

P. Williams, E Risk Sciences, LLP, Boulder, CO

Objective: Benzene exposures among vehicle mechanics in the United States and abroad were characterized using measured data and exposure modeling. These data, which have not been previously analyzed, may be used to assess benzene risks for mechanics exposed to gasoline or other petroleum derived products.

Methods: Time weighted average (TWA) and task based benzene concentrations were estimated based on published air sampling data and statistical analyses compared benzene concentrations by region, season, and job task. Also, the predictive ability of a mathematical model to estimate task based benzene concentrations under 216 gasoline and 384 aerosol spray cleaner scenarios was evaluated. The potential for dermal exposures among vehicle mechanics was discussed. Cumulative benzene exposures for mechanics with varying work histories were estimated.

Results: TWA airborne concentrations of benzene for vehicle mechanics in the United States averaged 0.01-0.05 ppm, since at least the late 1970s, with maximal TWA concentrations ranging from 0.03-0.38 ppm. Benzene exposures were notably lower in the summer than winter and in the Southwest compared to other geographic regions. Exposures were significantly higher during known gasoline related tasks such as changing fuel pump or filter. Measured benzene concentrations were greater for vehicle mechanics in other countries due to the higher benzene content of gasoline (5% vs. 1-2%) and other factors. Short-term airborne concentrations of benzene frequently exceeded 1 ppm during gasoline related tasks, but remained below 0.2 ppm for tasks involving other petroleum products. Application of a two zone model using reasonable input values yielded predicted task based benzene concentrations similar to those measured. Dermal exposures were found to contribute little to total exposure. Estimates of cumulative benzene exposure ranged from 0.5 to 1.5 ppm-years after the late 1970s, and 3.5 to 4.5 ppm-years before and after this time period.

Conclusions: Available data suggest that vehicle mechanics have not experienced significant exposures to benzene in the workplace, except perhaps during short-duration gasoline related tasks. Exposures are below occupational exposure limits and levels associated with an increased leukemia risk, but not necessarily for myelodysplastic syndrome (MDS) risk. These findings are consistent with epidemiology studies which have not demonstrated an increased risk of benzene induced health effects in this cohort of workers.



Give ‘Em a Break: Getting Aggressive with Understanding Brakes

F. Boelter, RHP Risk Management Inc., Boise, ID; J. Persky, RHP Risk Management Inc., Chicago, IL

Situation/Problem: Isaac Newton’s First Law states that a body in motion tends to stay in motion unless acted on by an outside force (1642-1726). If it moved, rotated, or slid, it would need to be stopped. Various types of Brakes were developed during the industrial revolution for our increasing use of powered mechanical equipment. In 1907, asbestos lined pads were used and outlasted other friction materials by a wide margin. Increased speeds, power and weight mandated further developments in wet and dry braking technology, but, linings do not last forever and need to be maintained and replaced.

Resolution: Our studies have examined the more aggressive brake activities involving drilling, grinding, compressed air, hammers, chisels and riveting. Maintaining and replacing brake linings involves numerous steps, situations, sizes, shapes, designs, and applications. The study on which we report relates to brake drums with shoes and to the process of arc grinding, a technique to obtain a perfect fit between the radius of the shoe and the radius of the drum which cannot be successfully achieved with hand tools. The arc grinding process involves two steps: turning the drum and arcing the shoe. A time and motion study was done on a professional mechanic while collecting personal TWA, EL, and area samples.

Results: During the course of 8 hours, a total of 8 jobs representing work on 13 axles were done. There were no visible emissions during the activities and all of the shoes were asbestos containing. Air samples were first analyzed for total fiber counts by NIOSH method 7400. The personal 8hrTWA total f/cc was 0.019 for the mechanic and 0.018 for the helper. Regarding personal 30-minute short term sampling, out of 32 total samples on the mechanic and helper, only 7 were above the LOQ and ranged from 0.049 to 0.086 total f/cc. Out of twenty 4-hour area samples, 17 were above the LOQ and ranged from 0.012 to 0.052 total f/cc.

Lessons learned: Studies regarding exposures are challenging to conduct and when examining historical products and methods, it is critical to have OEM parts, vintage equipment, and a knowledgeable tradesperson. While the relative risks are probably obvious, taking our study results into the arena of Big Data might incorporate transportation maps, vehicular densities on highways, NHTSA databases, fosterite, NOA, nonregulated amphiboles, and NOAA weather patterns, just to name a few. Perhaps through Big Data we will relearn the value of scientific parsimony and first order analysis.



Benchmark Dose Modeling for Respiratory Irritation from 2,3-Pentanedione Exposure

W. Cyrs, D. Dussex, A. Monnot, and M. Glynn, Cardno ChemRisk, San Francisco, CA

Objective: Beginning in the early 2000s, artificial butter flavorings have been scrutinized for their potential to produce adverse health effects. Of the numerous compounds in these flavorings, diacetyl has become the target of industrial hygiene monitoring and control efforts. When possible, it has been eliminated altogether and substituted with other flavoring chemicals, including 2,3-pentanedione (23PD). However, the potential toxicity of 23PD is questioned based on its structural similarity to diacetyl. There are no current occupational exposure limits (OELs) for 23PD. The objective of this research is to use benchmark dose modeling (BMD) of the available toxicological data to determine benchmark concentrations for 23PD.

Methods: All nine available models in EPA’s BMDS v. 2.6.0 modeling software were used to determine 23PD concentrations associated with a 10% excess risk (BMC10) of bronchial irritation and the 95% lower confidence limits (BMCL10). Modeled bronchial inflammation data were obtained from exposed rodents in the inhalation study with the longest exposure duration of 12 days. In that study, 11 to 12 mice were exposed to concentrations of 0, 50, 100, and 200 ppm 23PD each for 6 hours per day, and experienced minimal to mild inflammation.

Results: BMD analysis yielded BMC10s ranging from 3.3 to 13.8 ppm, and BMCL10s ranging from 0.5 to 9.7 ppm. Only 2 models fit the data well, judging by goodness-of-fit p-values greater than 0.1. The LogLogistic and LogProbit models produced BMC10s of 3.3 and 7.0 ppm, respectively, and BMCL10s of 0.5 and 4.2 ppm, respectively.

Conclusions: These results are similar, if not slightly lower, to those obtained by others for diacetyl, suggesting that 23PD might have similar if not greater toxicity. However, there are several notable problems with the data: most measured health effects had response rates of either 0% or 100%; the lowest response rate in the actual modeled data was high at 75%. Lastly, the modeled results were highly inconsistent. Because of these issues, an OEL development approach based on LOAEL to NOAEL extrapolation (e.g., 50 ppm ÷ 10) might be more appropriate than BMD analysis of these data. More importantly, a study with a greater number of exposed animals and exposure concentrations and a longer exposure period would likely provide better dose-response data upon which one could develop a health based OEL for 23PD.



Anthophyllite Asbestos: State of the Art Understanding of its Toxicological Properties

S. Gaffney, B. Simmons, M. Grespin, L. Garnick, and D. Paustenbach, Cardno ChemRisk, San Francisco, CA; A. Gauthier, Johns Hopkins University, Baltimore, MD

Objective: Anthophyllite is an amphibole form of asbestos. Historically, it was used in a limited number of products because of its lack of strength and brittle nature. No published resource currently exists that offers a complete understanding of anthophyllite toxicity and of its effect on exposed populations over time. Therefore, we performed a review of published and unpublished literature relating to anthophyllite, focusing on how its toxicity was scientifically understood through time, and how such knowledge fits into the larger context of asbestos research.

Methods: In this review, we conducted a comprehensive search of publically available documents that discussed the use, mining, properties, toxicity, exposure, and potential health effects of anthophyllite. Over 200 documents were identified, of which, 78 contained relevant and useful information that we present in this assessment, according to four different eras in time.

Results: Our analysis confirms that anthophyllite, including its potency and other toxicological properties, has not been well-studied. This is likely because of several factors: anthophyllite is a relatively rare form of amphibole; its use was historically minimal compared to other forms of asbestos; and it is often only included in studies as a component of mixed asbestos exposures (thus not making it possible to understand the pure form). Toxicology studies from the 1970s have indicated that, at sufficient doses, anthophyllite can potentially cause asbestosis, lung cancer, and mesothelioma. Studies of Finnish anthophyllite miners through the 1980s, though, found increased incidence of asbestosis and lung cancer, but not mesothelioma. It wasn’t until the mid-1990s that an epidemiological link with mesothelioma was observed.

Conclusions: Based on our assessment, we found that characterizing the true risks of anthophyllite is difficult. Distinguishing between its asbestiform and nonasbestiform mineral form is essential from both a toxicological and regulatory perspective. Anthophyllite’s toxicity has generally been assumed to be similar to other amphiboles, with the exception of 1980-1998, when ACGIH® set its TLV® the same as chrysotile, not amosite and crocidolite. Based on the limited amount of information available, for a better understanding of anthophyllite’s toxicity alone, significant additional study is needed.



Ebola and PPE: Developing a Protection Strategy

P. Lilley, US Army, 5158 Blackhawk Rd, MD

Situation/Problem: In 2014 Operation United Assistance was launched to aid with the Ebola Virus Disease (EVD) pandemic in West Africa. The Army had developed a plan for personal protective equipment (PPE) for the soldiers deploying, but had no clear guidance for staff at Military Treatment Facilities (MTF) located within the United States. It became evident that there would be the potential for EVD cases on military posts, with military deploying to EVD endemic areas.

Resolution: To facilitate a rapid and protective plan development, the Surgeon General of the Army requested that the Army Public Health Center (Provisional) and the United States Army Medical Research Institute of Infectious Diseases (USAMRID) collaborate. Based on the questionnaires developed for assessing the potential risk associated with individual EVD patient, a risk level was assigned and a three tiered approach for PPE usage was developed. The first tier would be minimal PPE for lower risk of EVD exposure, and each subsequent tier would be substantially more PPE for higher risk EVD exposure. It became evident due to the unfortunate cases of nosocomial EVD transmission, the process of donning and doffing was of critical importance. A detailed sequence for donning and doffing was provided for each tier level and training was given to MTF personnel.

Results: From the collaboration, a standardized system of PPE use was created a​​​nd employed across all army MTFs. This allowed for centralized purchasing and distribution of the EVD specific PPE. It also accommodated the mobility of army personnel in that every MTF was following the same broad procedures only modified for their physical setup.

Lessons learned: Through the active period of Operation United Assistance, it became clear that the initial understanding of PPE needs was inconsistent with the threat. It was determined that a more robust questionnaire would eliminate costly donning and doffing of higher levels of PPE. Also, clear communication and risk assessment is necessary when developing a PPE scheme to be applied to a group as large as the Army.



The Fluidized Bed Asbestos Segregator (FBAS) as a Risk Assessment Tool for Asbestos in Soil

E. Cahill, EMSL Analytical, Cinnaminson, NJ

Situation/Problem: With increasing awareness of the potential for exposure from asbestos contaminated soil, a growing number of remediation projects now include a focus on analysis of soil for asbestos content. Most analytical techniques focus on determining the overall percentage or concentration of asbestos, however this information provides little insight into risk. Soil has always been a problem matrix for microscopic analysis due to homogeneity and particle size issues. Various sample preparation and analysis approaches have been developed to address these issues but each approach has its own set of advantages and disadvantages. The two primary approaches involve either sieving or milling the sample prior to analysis. The sieving method separates the soil into a coarse, medium and fine fraction which aids in the detection of asbestos or asbestos containing material during analysis. The milling method reduces the soil sample’s particle size so that a representative sub-sample can be prepped to slide for a microscopic analysis..

Resolution: The Fluidized Bed Asbestos Segregator (FBAS) technique looks at asbestos in soil in a completely different way. With this approach a carefully controlled flow of air is passed through the dried sample. Any fibers that have been liberated are sampled via isokinetic sampling onto filter cassettes for direct preparation techniques and analysis by TEM. Analysis is typically performed by the ISO 10312 method and provides a result in respirable fibers per gram that can aid in risk assessment. The FBAS was originally designed by the Idaho National Laboratory. The EPA later improved the design of this instrument and performed numerous validation studies with blind prep and analysis of spiked samples. They have recently been using this technique on various soil related superfund sites.

Results: Through a Cooperative Research and Development Agreement (CRADA), the author is working with the EPA on various operational and design experiments and further validation. The data so far is showing a linear relationship between known asbestos concentrations of spiked samples and respirable fiber concentrations by FBAS.

Lessons learned: This presentation will provide an overview of the primary techniques used for soil analysis including the new FBAS. After this technical session, participants should walk away with a better understanding of the issues surrounding asbestos in soil as well as a firm knowledge of their sampling and analytical choices.​