Characterization of size-specific particulate matter emission rates for a simulated medical laser procedure--a pilot study.

Prior investigation on medical laser interaction with tissue has suggested device operational parameter settings influence laser generated air contaminant emission, but this has not been systematically explored. A laboratory-based simulated medical laser procedure was designed and pilot tested to determine the effect of laser operational parameters on the size-specific mass emission rate of laser generated particulate matter. Porcine tissue was lased in an emission chamber using two medical laser systems (CO2, λ = 10,600 nm; Ho:YAG, λ = 2100 nm) in a fractional factorial study design by varying three operational parameters (beam diameter, pulse repetition frequency, and power) between two levels (high and low) and the resultant plume was measured using two real-time size-selective particle counters. Particle count concentrations were converted to mass emission rates before an analysis of variance was used to determine the influence of operational parameter settings on size-specific mass emission rate. Particle shape and diameter were described for a limited number of samples by collecting particles on polycarbonate filters, and photographed using a scanning electron microscope (SEM) to examine method of particle formation. An increase in power and decrease in beam diameter led to an increase in mass emission for the Ho:YAG laser at all size ranges. For the CO2 laser, emission rates were dependent on particle size and were not statistically significant for particle ranges between 5 and 10 µm. When any parameter level was increased, emission rate of the smallest particle size range also increased. Beam diameter was the most influential variable for both lasers, and the operational parameters tested explained the most variability at the smallest particle size range. Particle shape was variable and some particles observed by SEM were likely created from mechanical methods. This study provides a foundation for future investigations to better estimate size-specific mass emission rates and particle characteristics for additional laser operational parameters in order to estimate occupational exposure, and to inform control strategies.

Application of a two-zone model to estimate medical laser-generated particulate matter exposures.

We estimated particulate matter exposures for two simulated medical laser procedures using a near-field/far-field model. Size-specific mass emission rates obtained from a laboratory-based emission chamber study were used with estimated room size, air exchange rate, and interflow between zones to demonstrate the potential exposure range. Modeled steady-state concentrations for the near-field ranged between 80 and 2140 µg/m(3) and between 40 and 1650 µg/m(3) in the far-field. Results indicate concentrations in the simulated scenarios are similar to those obtained from limited field assessments conducted in hospital operating rooms. Since new medical laser technologies and applications continue to grow, modeled occupational exposures of medical laser-generated particulate matter can be useful in better understanding these exposures in the clinical environment, and to inform control strategies.

Groundwater arsenic in Chimaltenango, Guatemala.

In the Municipality of Chimaltenango, Guatemala, we sampled groundwater for total inorganic arsenic. In total, 42 samples were collected from 27 (43.5%) of the 62 wells in the municipality, with sites chosen to achieve spatial representation throughout the municipality. Samples were collected from household faucets used for drinking water, and sent to the USA for analysis. The only site found to have a concentration above the 10 µg/L World Health Organization provisional guideline for arsenic in drinking water was Cerro Alto, where the average concentration was 47.5 µg/L. A health risk assessment based on the arsenic levels found in Cerro Alto showed an increase in noncarcinogenic and carcinogenic risks for residents as a result of consuming groundwater as their primary drinking water source. Using data from the US Geological Survey and our global positioning system data of the sample locations, we found Cerro Alto to be the only site sampled within the tertiary volcanic rock layer, a known source of naturally occurring arsenic. Recommendations were made to reduce the levels of arsenic found in the community's drinking water so that the health risks can be managed.

Modeled occupational exposures to gas-phase medical laser-generated air contaminants.

Exposure monitoring data indicate the potential for substantive exposure to laser-generated air contaminants (LGAC); however the diversity of medical lasers and their applications limit generalization from direct workplace monitoring. Emission rates of seven previously reported gas-phase constituents of medical laser-generated air contaminants (LGAC) were determined experimentally and used in a semi-empirical two-zone model to estimate a range of plausible occupational exposures to health care staff. Single-source emission rates were generated in an emission chamber as a one-compartment mass balance model at steady-state. Clinical facility parameters such as room size and ventilation rate were based on standard ventilation and environmental conditions required for a laser surgical facility in compliance with regulatory agencies. All input variables in the model including point source emission rates were varied over an appropriate distribution in a Monte Carlo simulation to generate a range of time-weighted average (TWA) concentrations in the near and far field zones of the room in a conservative approach inclusive of all contributing factors to inform future predictive models. The concentrations were assessed for risk and the highest values were shown to be at least three orders of magnitude lower than the relevant occupational exposure limits (OELs). Estimated values do not appear to present a significant exposure hazard within the conditions of our emission rate estimates.

A pilot study to determine medical laser generated air contaminant emission rates for a simulated surgical procedure.

The U.S. Occupational Safety and Health Administration (OSHA) estimates that half a million health-care workers are exposed to laser surgical smoke each year. The purpose of this study was to establish a methodology to (1) estimate emission rates of laser-generated air contaminants (LGACs) using an emission chamber, and to (2) perform a screening study to differentiate the effects of three laser operational parameters. An emission chamber was designed, fabricated, and assessed for performance to estimate the emission rates of gases and particles associated with LGACs during a simulated surgical procedure. Two medical lasers (Holmium Yttrium Aluminum Garnet [Ho:YAG] and carbon dioxide [CO2]) were set to a range of plausible medical laser operational parameters in a simulated surgery to pyrolyze porcine skin generating plume in the emission chamber. Power, pulse repetition frequency (PRF), and beam diameter were evaluated to determine the effect of each operational parameter on emission rate using a fractional factorial design. The plume was sampled for particulate matter and seven gas phase combustion byproduct contaminants (benzene, ethylbenzene, toluene, formaldehyde, hydrogen cyanide, carbon dioxide, and carbon monoxide): the gas phase emission results are presented here. Most of the measured concentrations of gas phase contaminants were below their limit of detection (LOD), but detectable measurements enabled us to determine laser operation parameter influence on CO2 emissions. Confined to the experimental conditions of this screening study, results indicated that beam diameter was statistically significantly influential and power was marginally statistically significant to emission rates of CO2 when using the Ho:YAG laser but not with the carbon dioxide laser; PRF was not influential vis-a-vis emission rates of these gas phase contaminants.

Laser-generated air contaminants from medical laser applications: a state-of-the-science review of exposure characterization, health effects, and control.

The clinical use of lasers in surgery began in 1973 with applications of the carbon dioxide laser in otolaryngology, and since then the use of lasers has become commonplace in many medical and surgical specialties. Nonetheless, when biological tissue is subjected to laser radiation, the target cells can be vaporized, resulting in the aerosolization of their contents and the subsequent exposure of health care workers to laser-generated air contaminants (LGACs). The purpose of our analysis was to summarize and present all of the published literature pertaining to the laser-induced plume chemical and physical composition, health effects, and methods of control. The objective was to identify knowledge gaps within exposure science to set a research agenda for the protection of health care personnel exposed to LGACs. A literature search was performed using the PubMed database using a variety of search strategies and keyword combinations. To locate additional studies, we systematically searched the reference lists of all studies identified by our search, as well as key review papers. To date, researchers have identified roughly 150 chemical constituents of plume, as well as fine and ultrafine particulate matter, which has been shown to include viable cellular material, viruses, and bacteria. However, very few studies have attempted to characterize the effects of laser system type, power, and tissue treated, as it relates to LGAC exposure. Furthermore, current control strategies do not appear to be adequate in preventing occupational exposure to LGACs.

Long-term health experience of jet engine manufacturing workers: III. Incidence of malignant central nervous system neoplasms.

OBJECTIVE: To explore a perceived unusual occurrence of glioblastoma at one jet engine manufacturing facility located in North Haven (NH), Connecticut (CT). METHODS: Subjects were 212,513 workers ever employed in 1 of 8 manufacturing facilities from 1952 to 2001 and at risk from 1976 to 2004. We identified 722 cases of CNS neoplasms mainly by tracing through 19 state cancer registries. We computed standardized incidence ratios (SIRs) based on CT state and national rates and modeled internal relative risks (RRs). RESULTS: We found overall deficits in cases for glioblastoma (275 cases, SIR = 0.77, CI = 0.68-0.87) and most other histology categories examined. NH workers had a not statistically significant overall 8% excess in glioblastoma (43 cases, SIR = 1.08, CI = 0.78-1.46). Salaried NH workers had a statistically significant twofold risk of glioblastoma compared with hourly workers (17 cases, RR = 2.04, CI = 1.15-3.57). Other subgroups of NH workers revealed elevated but not statistically significant glioblastoma risks but little evidence of an association with duration of employment or time since first employment. CONCLUSIONS: Incidence rates for glioblastoma and other malignant CNS neoplasm histologies were not elevated in the total cohort. The glioblastoma excesses observed among NH workers may reflect external occupational factors, non-occupational factors or workplace factors unique to NH unmeasured in the current study.

Methodological issues in a retrospective cancer incidence study.

The authors traced incidence of central nervous system cancer in a large occupational cohort of jet engine manufacturing workers from 1976 to 2004 in the 24 US states that comprised 95% of the cohort deaths. The cohort of approximately 224,000 employees was matched with cancer registry data; all central nervous system cancer matches were requested with their diagnostic data. This paper highlights the obstacles encountered while conducting this retrospective cancer incidence study. The authors spent approximately 700 hours completing applications and obtaining the cohort matches. Approximately 70% of the cases were identified in the state in which the facility of interest is located. In addition to the large amount of time involved, identified issues include complicated approval processes, high costs, temporal differences among the registries, and registry agency difficulty in performing the matching. Several states do not allow individual-level data to be used for research purposes. Researchers can gain important cancer incidence information by matching retrospective cohorts to multiple state cancer registries. However, they should carefully weigh the time and costs required and plan accordingly. Despite some serious obstacles, many of which are potentially resolvable, cancer incidence studies of retrospective cohorts using multiple cancer registries are feasible.

Risk perception and water purification practices for water-borne parasitic infections in remote Nepal.

This study assesses water-borne infection risk perception and water boiling habits in a remote Sankhuwasava region of Nepal using a brief interview-style questionnaire. All subjects were aware of the risks associated with drinking unpurified water, but a majority (65%) reported they did not boil water regularly, and almost 60% of villagers interviewed had history of infection despite their boiling practices. In contrast to reports from other communities in Nepal, risk awareness was sufficient in this region. Water boiling alone did not confer protection. Future efforts should target sanitation, screening, and other sources of contamination.

Undergraduate Environmental Public Health Education.

Environmental, occupational, and public health in the United States are practiced across a fragmented system that makes work across those areas more difficult. A large proportion of currently active environmental and occupational health professionals, advocates, policy makers, and activists are nearing retirement age, while some of our major health challenges are heavily influenced by aspects of environment. Concurrently, programs that educate undergraduate college students in environmental health are faced with multiple, often competing demands which can impede progressive movement toward dynamic curricula for the needs of the twenty-first century. We describe our use of developmental evaluation to negotiate these challenges in our specific undergraduate education program, with the dual aims of drawing attention to developmental evaluation as a useful tool for people involved in environmental and occupational health advocacy, policy-making, activism, research, or education for change, as well as to promote discussion about how best to educate the next generation of environmental public health students.

Dust emission rates from food processing.

A field study was performed to develop emission rates for dust exposure at a food processing facility. Eight 2-hour periods were monitored over 2 days. Area total suspended particulate samples were collected on 37 mm polyvinyl chloride filters with 5 mum pore size according to NIOSH Method 0500. Filters were analyzed gravimetrically. Ventilation and production activity data were collected during air sampling. Two mass balance models were used to calculate emission rates. The first was an experimental mass balance model, with the mass of contaminant generated determined by air flow and concentration measurements at room exit and entry points. The second treated the work environment as a completely mixed space, utilizing ventilation and area concentration measurements. Emission rates generated from mass balance models ranged from 2.09-542 mg/min for the various processing operations and food products. Process emission rates with production activity data allow estimation of dust exposure in similar facilities, and help direct development of exposure control strategies.

Biomarkers of Human Cardiopulmonary Response After Short-Term Exposures to Medical Laser-Generated Particulate Matter From Simulated Procedures: A Pilot Study.

OBJECTIVE: We conducted an exposure chamber study in humans using a simulated clinical procedure lasing porcine tissue to demonstrate evidence of effects of exposure to laser-generated particulate matter (LGPM). METHODS: We measured pre- and post-exposure changes in exhaled nitric oxide (eNO), spirometry, heart rate variability (HRV), and blood markers of inflammation in five volunteers. RESULTS: Change in pre- and post-exposure measurements of eNO and spirometry was unremarkable. Neutrophil and lymphocyte counts increased and fibrinogen levels decreased in four of the five subjects. Measures of HRV showed decreases in the standard deviation of normal between beat intervals and sequential 5-minute intervals. CONCLUSION: These data represent the first evidence of human physiologic response to LGPM exposure. Further exploration of coagulation effects and HRV is warranted.

Long-term health experience of jet engine manufacturing workers: VII: occupational exposures.

OBJECTIVE: To reconstruct agent-specific occupational exposures for a cohort of jet engine manufacturing workers for use in an epidemiological mortality study. METHODS: Potential chemical and physical exposures at eight jet engine manufacturing and overhaul/repair plants were evaluated for the period 1952 to 2001. Eleven agents were selected for detailed examination, and a job-exposure matrix was constructed. RESULTS: Quantitative exposure estimates were generated for metalworking fluids, nickel, cobalt, chromium, solvents, and incomplete combustion aerosol from metalworking fluids. Qualitative exposure estimates were assigned for ionizing radiation, electromagnetic fields, polychlorinated biphenyls, and lead-cadmium. All exposures showed decreasing trends over the study period. CONCLUSIONS: The quantitative exposure levels generated in this study were lower than early contemporaneous professional practice recommendations and were similar to or lower than published data from other industries.

Long-term health experience of jet engine manufacturing workers: IX. further investigation of general mortality patterns in relation to workplace exposures.

OBJECTIVE: To evaluate mortality rates among a cohort of jet engine manufacturing workers. METHODS: Subjects were 222,123 workers employed from 1952 to 2001. Vital status was determined through 2004 for 99% of subjects and cause of death for 95% of 68,317 deaths. We computed standardized mortality ratios and modeled internal cohort rates. RESULTS: Mortality excesses reported initially no longer met the criteria for further investigation. We found two chronic obstructive pulmonary disease-related mortality excesses that met the criteria in two of eight study plants. CONCLUSIONS: At the total cohort level, chronic obstructive pulmonary disease-related categories were not related to any factors or occupational exposures considered. A full evaluation of these excesses was limited by lack of data on smoking history. Occupational exposures received outside of work or uncontrolled positive confounding by smoking cannot be ruled out as reasons for these excesses.

Photodynamic therapy: occupational hazards and preventative recommendations for clinical administration by healthcare providers.

OBJECTIVE: Photodynamic therapy (PDT) as a medical treatment for cancers is an increasing practice in clinical settings, as new photosensitizing chemicals and light source technologies are developed and applied. PDT involves dosing patients with photosensitizing drugs, and then exposing them to light using a directed energy device in order to manifest a therapeutic effect. Healthcare professionals providing PDT should be aware of potential occupational health and safety hazards posed by these treatment devices and photosensitizing agents administered to patients. MATERIALS AND METHODS: Here we outline and identify pertinent health and safety considerations to be taken by healthcare staff during PDT procedures. RESULTS: Physical hazards (for example, non-ionizing radiation generated by the light-emitting device, with potential for skin and eye exposure) and chemical hazards (including the photosensitizing agents administered to patients that have the potential for exposure via skin, subcutaneous, ingestion, or inhalation routes) must be considered for safe use of PDT by the healthcare professional. CONCLUSIONS: Engineering, administrative, and personal protective equipment controls are recommendations for the safe use and handling of PDT agents and light-emitting technologies.

Long-term health experience of jet engine manufacturing workers: VI: incidence of malignant central nervous system neoplasms in relation to estimated workplace exposures.

OBJECTIVE: To determine whether glioblastoma (GB) incidence rates among jet engine manufacturing workers were associated with specific chemical or physical exposures. METHODS: Subjects were 210,784 workers employed from 1952 to 2001. We conducted a cohort incidence study and two nested case-control studies with focus on the North Haven facility where we previously observed a not statistically significant overall elevation in GB rates. We estimated individual-level exposure metrics for 11 agents. RESULTS: In the total cohort, none of the agent metrics considered was associated with increased GB risk. The GB incidence rates in North Haven were also not related to workplace exposures, including the "blue haze" exposure unique to North Haven. CONCLUSIONS: If not due to chance alone, GB rates in North Haven may reflect external occupational factors, nonoccupational factors, or workplace factors unique to North Haven unmeasured in the current evaluation.

Long-term health experience of jet engine manufacturing workers: VIII. glioblastoma incidence in relation to workplace experiences with parts and processes.

OBJECTIVE: To determine whether glioblastoma (GB) incidence rates among jet engine manufacturing workers were associated with workplace experiences with specific parts produced and processes performed. METHODS: Subjects were 210,784 workers employed between 1952 and 2001. We conducted nested case-control and cohort incidence studies with focus on 277 GB cases. We estimated time experienced with 16 part families, 4 process categories, and 32 concurrent part-process combinations with 20 or more GB cases. RESULTS: In both the cohort and case-control studies, none of the part families, process categories, or both considered was associated with increased GB risk. CONCLUSIONS: If not due to chance alone, the not statistically significantly elevated GB rates in the North Haven plant may reflect external occupational factors or nonoccupational factors unmeasured in the current evaluation.

An assessment of the occupational hazards related to medical lasers.

OBJECTIVE: Occupational hazards associated with medical laser applications remain poorly understood and uncharacterized. METHODS: A literature search was performed using PubMed, and all articles relevant to beam and nonbeam medical laser hazards were reviewed. The Rockwell Laser Industries Laser Accident Database was searched for medical laser injuries and abstracted. RESULTS: Eye injuries, skin burns, injuries related to the onset of fires, and electric shock have been reported in relation to medical laser use. It is probable that both acute and chronic health effects have been experienced by medical personnel as the result of exposure to laser generated air contaminants. CONCLUSIONS: Because of the clinical benefits they provide, the growth of laser technologies and applications are anticipated to result in an increase in the number and type of medical personnel with future exposure to laser hazards.