Last data update: Jan 27, 2025. (Total: 48650 publications since 2009)
Records 1-14 (of 14 Records) |
Query Trace: Streicher R[original query] |
---|
Characterizing dynamic atmosphere generation system performance for analytical method development
Doepke A , Streicher RP , Shaw PB , NAndrews R , Farwick DR , Westbrook EG , Roberts JL , O'Connor PF , Stastny AL , Kulkarni PS . J Occup Environ Hyg 2024 1-13 A significant portion of the work of developing and validating methods for volatile organic compound (VOC) sampling in workplace atmospheres involves the use of laboratory-generated atmospheres. The sample variability was evaluated from the dynamic atmosphere generation system used for VOC atmosphere generation and sampling. Characterization of the bias and variability of samples was done for a variety of atmospheres containing neat n-heptane and mixtures of VOCs sampled on activated coconut shell charcoal. Estimates of sampling variability ranged from 2% for neat n-heptane to 12% for a component in the 10 VOC mix. Sample variability increased for lower concentration samples and for mixtures of VOCs compared to single component atmospheres. This study can serve as a baseline for future atmosphere sampling experiments evaluating performance at lower concentrations and mixed VOC environments. |
Evaluation of propylene glycol methyl ether as a potential challenge agent for leak detection of liquid and headspace from closed system drug transfer devices using Fourier transform infrared spectroscopy
Westbrook EG , Doepke A , Streicher RP . Anal Methods 2022 14 (43) 4393-4407 Choosing an appropriate surrogate of hazardous drugs for use in testing Closed System Drug-Transfer Devices (CSTDs) is a challenging endeavor with many factors that must be considered. It was suggested that the compound propylene glycol methyl ether (PGME) may meet many of the criteria we considered important in a suitable surrogate. Criteria included sufficient volatility to evaporate from aqueous liquid leaks efficiently, a Henry's constant which produced sufficient vapor phase concentrations to make headspace leaks detectable, and suitability for detection using a low-cost detection system. We evaluated the measurement of vapors from solutions containing PGME released inside a closed chamber. We present data used to quantify limits of detection, limits of quantification, bias, precision, and accuracy of Fourier Transform Infrared Spectroscopy (FTIR) measurements of vapors from 2.5 M PGME solutions. The effects of ethanol as a component of the PGME solution were also evaluated. Liquid drops of PGME solutions and headspace vapors above PGME solutions were released to simulate leaks from CSTDs. Using a calibration apparatus, an instrumental limit of detection (LOD) of 0.25 ppmv and a limit of quantitation (LOQ) of 0.8 ppmv were determined for PGME vapor. A LOD of 1.1 μL and a LOQ of 3.5 μL were determined for liquid aliquots of 2.5 M PGME solution released in a closed chamber. Accurate quantitation of liquid leaks required complete evaporation of droplets. With the upper end of the useable quantitation range limited by slow evaporation of relatively large droplets and the lower end defined by the method LOQ, the method evaluated in this research had a narrow quantitative range for liquid droplets. Displacement of 45 mL of vial headspace containing PGME vapor is the largest amount expected when using the draft NIOSH testing protocol. Release of an unfiltered 45 mL headspace aliquot within the NIOSH chamber was calculated to produce a concentration of 0.8 ppmv based on the Henry's constant, which is right at the instrumental LOQ. Therefore, the sensitivity of the method was not adequate to determine leaks of PGME vapor from a headspace release through an air filtering CSTD when using the draft NIOSH testing protocols with an FTIR analyzer. |
Method development for onsite monitoring of volatile organic compounds via portable TDGC-MS: evaluation of the analytical performances of HAPSITE ER instrumentation and thermal desorption sampling media
Smith ME , Westbrook E , Stastny AL , Streicher RP , Elliott MG . Int J Environ Anal Chem 2022 1-18 Determining worker exposure to hazardous volatile organic compounds (VOCs) in air at levels exceeding the Permissible Exposure Limits and Recommended Exposure Limits established by the U.S. federal agencies of Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH), respectively, will continue to be an important part of environmental and occupational health risk assessments. The purpose of this work was to develop a reliable analytical method for rapid and on-site assessments of occupational VOC exposures using field-capable thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) instrumentation (i.e. the HAPSITE ER). The experiments involved in this study included determining TD-GC-MS parameters suitable for efficient analyte separation and quantitation on the HAPSITE ER, determinations of analyte mass loadings that cause mass spectrometer detector saturations, generation of calibration curves, estimations of the limits of detection (LODs) and quantification (LOQs), as well as desorption efficiency and relative response factor repeatability. The LODs using Carbopack B and Tenax TA sampling media were estimated and ranged from 0.21.9 ng and 0.0450.3 ng, respectively. The LOQs using Carbopack B and Tenax TA sampling media were estimated and ranged from 1.06.3 ng and 0.21.1 ng, respectively. We have developed a reliable analytical method for chloroform, benzene, trichloroethylene, and heptane using field-portable HAPSITE ER instrumentation and Tenax TA sorbent media. Reliable and accurate methods were developed for chloroform and trichloroethylene using Carbopack B sorbent media, however, this particular sorbent hadlow desorption efficiency and insufficient repeatability in relative response factors for many analytes. Our current and ongoing work in determining the uptake rates for analytes on Tenax TA sorbent media will make the methods described herein applicable for on-site occupational VOC exposure assessments of chloroform, benzene, trichloroethylene, and heptane using either passive or active air sampling techniques. This work was authored as part of the Contributors official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 USC 105, no copyright protection is available for such works under US Law. |
A field-portable colorimetric method for the measurement of peracetic acid vapors: A comparison of glass and plastic impingers
Stastny AL , Doepke A , Streicher RP . J Occup Environ Hyg 2022 19 (8) 1-13 A method for measuring peracetic acid vapors in air using impinger sampling and field-portable colorimetric analysis is presented. The capture efficiency of aqueous media in glass and plastic impingers was evaluated when used for peracetic acid vapor sampling. Measurement of peracetic acid was done using an N,N-diethyl-p-phenylenediamine colorimetric method with a field portable spectrometer. The linearity of the N,N-diethyl-p-phenylenediamine method was determined for peracetic acid both in-solution and captured from vapor phase using glass or plastic impingers. The Limits of Detection for the glass and plastic impingers were 0.24 mg/m(3) and 0.28 mg/m(3), respectively, for a 15 L air sample. The Limits of Quantitation were 0.79 mg/m(3) and 0.92 mg/m(3) for the glass and plastic impingers, respectively. Both metrics were below the American Conference of Governmental Industrial Hygienists Threshold Limit Value Short-Term Exposure Limit of 1.24 mg/m(3) (0.4 ppmv) during a 15-minute period. This impinger sampling method presented herein allows for an easy to use and rapid in-field measurement that can be used for evaluating occupational exposure to peracetic acid. |
Source apportionment and quantification of liquid and headspace leaks from closed system drug-transfer devices via Selected Ion Flow Tube Mass Spectrometry (SIFT-MS)
Doepke A , Streicher RP . PLoS One 2021 16 (11) e0258425 A system to differentiate and quantify liquid and headspace vapor leaks from closed system drug-transfer devices (CSTDs) is presented. CSTDs are designed to reduce or eliminate hazardous drug (HD) exposure risk when compounding and administering HDs. CSTDs may leak liquid, headspace, or a mixture of the two. The amount of HD contained in liquid and headspace leaks may be substantially different. Use of a test solution containing two VOCs with differences in ratios of VOC concentrations in the headspace and liquid enables source apportionment of leaked material. SIFT-MS was used to detect VOCs from liquid and headspace leaks in the vapor phase. Included in this report is a novel method to determine the origin and magnitude of leaks from CSTDs. A limit of leak detection of 24 μL of headspace vapor and 0.14 μL of test liquid were found using Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). |
Controlled generation of peracetic acid atmospheres for the evaluation of chemical samplers
Doepke A , Stastny AL , Streicher RP . Anal Methods 2021 13 (34) 3799-3805 A system for controlled generation of peracetic acid (PAA) atmospheres used to test and evaluate sampling and measurement devices was developed and characterized. Stable atmospheric conditions were maintained in a dynamic flow system for hours while multiple sensors were simultaneously exposed to equivalent atmospheres of PAA vapors. Atmospheres characterized by a range of PAA concentrations at a controlled flow rate, temperature, and humidity were generated. Presented herein is a system for vaporization of PAA solutions to generate controlled atmospheres with less than 3% relative standard deviation (RSD) of the PAA concentrations over time. |
A landscape of genomic alterations at the root of a near-untreatable tuberculosis epidemic.
Klopper M , Heupink TH , Hill-Cawthorne G , Streicher EM , Dippenaar A , de Vos M , Abdallah AM , Limberis J , Merker M , Burns S , Niemann S , Dheda K , Posey J , Pain A , Warren RM . BMC Med 2020 18 (1) 24 ![]() ![]() BACKGROUND: Atypical Beijing genotype Mycobacterium tuberculosis strains are widespread in South Africa and have acquired resistance to up to 13 drugs on multiple occasions. It is puzzling that these strains have retained fitness and transmissibility despite the potential fitness cost associated with drug resistance mutations. METHODS: We conducted Illumina sequencing of 211 Beijing genotype M. tuberculosis isolates to facilitate the detection of genomic features that may promote acquisition of drug resistance and restore fitness in highly resistant atypical Beijing forms. Phylogenetic and comparative genomic analysis was done to determine changes that are unique to the resistant strains that also transmit well. Minimum inhibitory concentration (MIC) determination for streptomycin and bedaquiline was done for a limited number of isolates to demonstrate a difference in MIC between isolates with and without certain variants. RESULTS: Phylogenetic analysis confirmed that two clades of atypical Beijing strains have independently developed resistance to virtually all the potent drugs included in standard (pre-bedaquiline) drug-resistant TB treatment regimens. We show that undetected drug resistance in a progenitor strain was likely instrumental in this resistance acquisition. In this cohort, ethionamide (ethA A381P) resistance would be missed in first-line drug-susceptible isolates, and streptomycin (gidB L79S) resistance may be missed due to an MIC close to the critical concentration. Subsequent inadequate treatment historically led to amplification of resistance and facilitated spread of the strains. Bedaquiline resistance was found in a small number of isolates, despite lack of exposure to the drug. The highly resistant clades also carry inhA promoter mutations, which arose after ethA and katG mutations. In these isolates, inhA promoter mutations do not alter drug resistance, suggesting a possible alternative role. CONCLUSION: The presence of the ethA mutation in otherwise susceptible isolates from ethionamide-naive patients demonstrates that known exposure is not an adequate indicator of drug susceptibility. Similarly, it is demonstrated that bedaquiline resistance can occur without exposure to the drug. Inappropriate treatment regimens, due to missed resistance, leads to amplification of resistance, and transmission. We put these results into the context of current WHO treatment regimens, underscoring the risks of treatment without knowledge of the full drug resistance profile. |
Assessment of spray polyurethane foam worker exposure to organophosphate flame retardants through measures in air, hand wipes, and urine
Estill CF , Slone J , Mayer AC , Phillips K , Lu J , Chen IC , Christianson A , Streicher R , Guardia MJ , Jayatilaka N , Ospina M , Calafat AM . J Occup Environ Hyg 2019 16 (7) 1-12 Tris(1-chloro-2-propyl) phosphate (TCPP, also referenced as TCIPP), a flame retardant used in spray polyurethane foam insulation, increases cell toxicity and affects fetal development. Spray polyurethane foam workers have the potential to be exposed to TCPP during application. In this study, we determined exposure to TCPP and concentrations of the urinary biomarker bis(1-chloro-2-propyl) phosphate (BCPP) among 29 spray polyurethane foam workers over 2 work days. Work was conducted at residential or commercial facilities using both open-cell (low density) and closed-cell (high density) foam. Study participants provided two personal air samples (Day 1 and Day 2), two hand wipe samples (Pre-shift Day 2 and Post-shift Day 2), and two spot urine samples (Pre-shift Day 1 and Post-shift Day 2). Bulk samples of cured spray foam were also analyzed. Sprayers were found to have significantly higher TCPP geometric mean (GM) concentration in personal air samples (87.1 mug/m(3)), compared to helpers (30.2 mug/m(3); p = 0.025). A statistically significant difference was observed between TCPP pre- and post-shift hand wipe GM concentrations (p = 0.004). Specifically, TCPP GM concentration in post-shift hand wipe samples of helpers (106,000 ng/sample) was significantly greater than pre-shift (27,300 ng/sample; p < 0.001). The GM concentration of the urinary biomarker BCPP (23.8 mug/g creatinine) was notably higher than the adult male general population (0.159 mug/g creatinine, p < 0.001). Urinary BCPP GM concentration increased significantly from Pre-shift Day 1 to Post-shift Day 2 for sprayers (p = 0.013) and helpers (p = 0.009). Among bulk samples, cured open-cell foam had a TCPP GM concentration of 9.23% by weight while closed-cell foam was 1.68%. Overall, post-shift BCPP urine concentrations were observed to be associated with TCPP air and hand wipe concentrations, as well as job position (sprayer vs. helper). Spray polyurethane foam workers should wear personal protective equipment including air-supplied respirators, coveralls, and gloves during application. |
Occupational Exposures to New Drycleaning Solvents: High-flashpoint Hydrocarbons and Butylal
Ceballos DM , Whittaker SG , Lee EG , Roberts J , Streicher R , Gong FN , Broadwater W , Broadwater K . J Occup Environ Hyg 2016 13 (10) 0 The drycleaning industry is moving away from using perchloroethylene. Occupational exposures to two alternative drycleaning solvents, butylal and high-flashpoint hydrocarbons, have not been well-characterized. We evaluated four drycleaning shops that used these alternative solvents. The shops were staffed by Korean- and Cantonese-speaking owners, and Korean-, Cantonese-, and Spanish-speaking employees. Because most workers had limited English proficiency we used language services in our evaluations. In two shops we collected personal and area air samples for butylal. We also collected air samples for formaldehyde and butanol, potential hydrolysis products of butylal. Because there are no occupational exposure limits for butylal, we assessed employee health risks using control banding tools. In the remaining two shops we collected personal and area air samples for high-flashpoint hydrocarbon solvents. In all shops the highest personal airborne exposures occurred when workers loaded and unloaded the drycleaning machines and pressed drycleaned fabrics. The air concentrations of formaldehyde and butanol in the butylal shops were well below occupational exposure limits. Likewise, the air concentrations of high-flashpoint hydrocarbons were also well below occupational exposure limits. However, we saw potential skin exposures to these chemicals. We provided recommendations on appropriate work practices and the selection and use of personal protective equipment. These recommendations were consistent with those derived using control banding tools for butylal. However, there is insufficient toxicological and health information to determine the safety of butylal in occupational settings. Independent evaluation of the toxicological properties of these alternative drycleaning solvents, especially butylal, is urgently needed. |
Genetic Determinants of Drug Resistance in Mycobacterium tuberculosis and Their Diagnostic Value.
Farhat MR , Sultana R , Iartchouk O , Bozeman S , Galagan J , Sisk P , Stolte C , Nebenzahl-Guimaraes H , Jacobson K , Sloutsky A , Kaur D , Posey J , Kreiswirth BN , Kurepina N , Rigouts L , Streicher EM , Victor TC , Warren RM , van Soolingen D , Murray M . Am J Respir Crit Care Med 2016 194 (5) 621-30 ![]() BACKGROUND: The development of molecular diagnostics that detect both the presence of Mycobacterium tuberculosis in clinical samples and drug resistance-conferring mutations promises to revolutionize patient care and interrupt transmission by ensuring early diagnosis. However, these tools require the identification of genetic determinants of resistance to the full range of anti-tuberculosis drugs. OBJECTIVES: To determine the optimal molecular approach needed, we sought to create a comprehensive catalogue of resistance mutations and assess their sensitivity and specificity in diagnosing drug resistance. METHODS: We developed and validated molecular inversion probes for DNA capture and deep sequencing of 28 drug resistance loci in M.tuberculosis. We used the probes for targeted sequencing of a geographically diverse set of 1397 clinical M.tuberculosis isolates with known drug resistance phenotypes. We identified a minimal set of mutations to predict resistance to first- and second-line anti-tuberculosis drugs and validated our predictions in an independent dataset. We constructed and piloted a web-based database that provides public access to the sequence data and prediction tool. RESULTS: The predicted resistance to rifampicin and isoniazid exceeded 90% sensitivity and specificity, but was lower for other drugs. The number of mutations needed to diagnose resistance is large and for the 13 drugs studied it was 238 across 18 genetic loci. CONCLUSION: These data suggest that a comprehensive M.tuberculosis drug resistance diagnostic will need to allow for a high dimension of mutation detection. They also support the hypothesis that currently unknown genetic determinants, potentially discoverable by whole genome sequencing, encode resistance to second-line TB drugs. |
Mycobacterium tuberculosis pncA polymorphisms that do not confer pyrazinamide resistance at a breakpoint concentration of 100 µg/ml in MGIT.
Whitfield MG , Warren RM , Streicher EM , Sampson SL , Sirgel FA , van Helden PD , Mercante A , Willby M , Hughes K , Birkness K , Morlock G , van Rie A , Posey JE . J Clin Microbiol 2015 ![]() Sequencing of the Mycobacterium tuberculosis pncA gene allows for pyrazinamide susceptibility testing. We summarize data on pncA polymorphisms which do not confer resistance at a susceptibility breakpoint of 100 mug/ml pyrazinamide in MGIT within a cohort of isolates from South Africa and the US Centre for Disease Control. |
Isocyanates and human health: multistakeholder information needs and research priorities
Lockey JE , Redlich CA , Streicher R , Pfahles-Hutchens A , Hakkinen PB , Ellison GL , Harber P , Utell M , Holland J , Comai A , White M . J Occup Environ Med 2015 57 (1) 44-51 OBJECTIVES: To outline the knowledge gaps and research priorities identified by a broad base of stakeholders involved in the planning and participation of an international conference and research agenda workshop on isocyanates and human health held in Potomac, Maryland, in April 2013. METHODS: A multimodal iterative approach was used for data collection including preconference surveys, review of a 2001 consensus conference on isocyanates, oral and poster presentations, focused break-out sessions, panel discussions, and postconference research agenda workshop. RESULTS: Participants included representatives of consumer and worker health, health professionals, regulatory agencies, academic and industry scientists, labor, and trade associations. CONCLUSIONS: Recommendations were summarized regarding knowledge gaps and research priorities in the following areas: worker and consumer exposures; toxicology, animal models, and biomarkers; human cancer risk; environmental exposure and monitoring; and respiratory epidemiology and disease, and occupational health surveillance. |
Genomic analysis identifies targets of convergent positive selection in drug-resistant Mycobacterium tuberculosis
Farhat MR , Shapiro BJ , Kieser KJ , Sultana R , Jacobson KR , Victor TC , Warren RM , Streicher EM , Calver A , Sloutsky A , Kaur D , Posey JE , Plikaytis B , Oggioni MR , Gardy JL , Johnston JC , Rodrigues M , Tang PK , Kato-Maeda M , Borowsky ML , Muddukrishna B , Kreiswirth BN , Kurepina N , Galagan J , Gagneux S , Birren B , Rubin EJ , Lander ES , Sabeti PC , Murray M . Nat Genet 2013 45 (10) 1183-9 ![]() M. tuberculosis is evolving antibiotic resistance, threatening attempts at tuberculosis epidemic control. Mechanisms of resistance, including genetic changes favored by selection in resistant isolates, are incompletely understood. Using 116 newly sequenced and 7 previously sequenced M. tuberculosis whole genomes, we identified genome-wide signatures of positive selection specific to the 47 drug-resistant strains. By searching for convergent evolution-the independent fixation of mutations in the same nucleotide position or gene-we recovered 100% of a set of known resistance markers. We also found evidence of positive selection in an additional 39 genomic regions in resistant isolates. These regions encode components in cell wall biosynthesis, transcriptional regulation and DNA repair pathways. Mutations in these regions could directly confer resistance or compensate for fitness costs associated with resistance. Functional genetic analysis of mutations in one gene, ponA1, demonstrated an in vitro growth advantage in the presence of the drug rifampicin. |
Communities near toluene diisocyanate sources: an investigation of exposure and health
Wilder LC , Langley RL , Middleton DC , Ernst K , Lummus ZL , Streicher RP , Campbell DS , Wattigney WA , Bernstein JA , Bernstein DI , Dearwent SM . J Expo Sci Environ Epidemiol 2011 21 (6) 587-94 Toluene diisocyanate (TDI) is a well-known cause of occupational asthma, but we know little about the potential for exposure and health effects among residents who live near facilities that release TDI. In the mid-1990's, the North Carolina Department of Health and Human Services and the Agency for Toxic Substances and Disease Registry investigated exposures to TDI and health outcomes in one community, which left some unanswered questions. This cross-sectional study evaluated the potential associations between living near a TDI source and the prevalence of three variables: asthma or asthma-like respiratory symptoms, antibodies specific to TDI, and verifiable levels of TDI in residential air. Results among North Carolina residents living near such facilities (five target communities) were compared with the results from residents living further away (five comparison communities). Overall, the prevalence of reporting either asthma or asthma-like respiratory symptoms was higher (odds ratio=1.60; 95% confidence interval=0.97-2.54) among residents in target communities than those in comparison communities. However, this difference was not statistically significant. Symptom prevalence varied greatly among the community populations. The prevalence of respiratory symptoms was higher near facilities with historically higher TDI emissions. Among the 351 participants who provided blood samples, only one had immunoglobulin G specific antibodies to TDI. This participant lived in a target area and may have had non-occupational exposure. TDI was detected at an extremely low level (1 ppt) in one of the 45 air samples from target communities. One ppt is one-tenth the EPA reference concentration. Overall, air sample and antibody test results are not consistent with recent or ongoing exposure to TDI. Journal of Exposure Science and Environmental Epidemiology advance online publication, 23 February 2011; doi:10.1038/jes.2011.5. |
- Page last reviewed:Feb 1, 2024
- Page last updated:Jan 27, 2025
- Content source:
- Powered by CDC PHGKB Infrastructure