Chronic low-level hydrogen sulfide exposure and potential effects on human health: a review of the epidemiological evidence.

The effects of exposure to high concentrations of hydrogen sulfide (H2S) on human health are well known. However, the potential human health hazards posed by low-level chronic environmental H2S exposure are being debated. Accordingly, we reviewed the literature regarding the effects of chronic, environmentally-relevant H2S exposures on human health. All human observational studies using an analytical study design (e.g. cohort, cross-sectional, case-control) to evaluate chronic-duration low-level H2S exposure (approximately ≤ 10 ppm on average, for 1 year or more), were evaluated for a range of health outcomes. Respiratory symptoms in both adults and children were the most consistently reported symptoms on the increase. When reported, such effects appear to be temporary, given that there is no consistent evidence of pulmonary function deficit in either age group, among those chronically exposed to low H2S concentrations. While sparse, some data also suggest potential ocular symptoms and disorders associated with chronic ambient level H2S exposure in adults (not children), but the limited data on H2S exposures, co-exposures and/or strong odor stimulus of H2S, temper interpretation. Neurological symptoms and deficits have been reported in some studies, but the highest quality evidence, obtained using objective outcome measures and a reasonably detailed assessment of exposure, does not support a neurological-related risk in adults (only one study in children). For the other endpoints assessed (cardiovascular, reproductive and developmental, and carcinogenicity), the results were mixed and/or conflicting, but did not indicate a potential health hazard, although this literature has several major limitations, particularly with regard to exposure estimation and the ability to assess exposure-response.

Hospital-Based Case-Control Study of MDS Subtypes and Benzene Exposure in Shanghai.

OBJECTIVE: Due to the sparse data on benzene exposure and myelodysplastic syndrome (MDS) subtypes, we studied this relationship in patients from 29 hospitals in Shanghai, China. METHODS: We recruited 604 cases of MDS and 1193 controls matched on age, sex, and admission date. We interviewed subjects for information on workplace and lifestyle exposures, and developed semi-quantitative exposure estimates. RESULTS: Benzene exposure showed a direct exposure-response pattern with refractory cytopenia with multilineage dysplasia, a less certain association with refractory cytopenia with unilineage dysplasia, and no association with other MDS subtypes. A different pattern was observed with farm residence and smoking, which was primarily related to refractory anemias. CONCLUSIONS: This research demonstrates the importance of MDS subtype specification for more robust etiologic insights. Our data suggests that subtypes with non-erythroid dysplasia are associated with benzene exposure.

Preventing G-induced loss of consciousness: 20 years of operational experience.

INTRODUCTION: Although anecdotal reports of G-induced loss of consciousness (G-LOC) in military aviation date back to before 1920, regular reporting did not begin until 1982. The effectiveness in the operational setting of G-LOC preventive measures, such as positive pressure breathing for G protection (PBG), has not been studied. METHODS: We use the term "crash" to represent an event where the aircraft was destroyed and "incident" to define those events where the crew reported a G-LOC episode and the aircraft was not damaged. Data on G-LOC crashes, incidents, and aircraft sorties (number of take-offs) were obtained from the USAF Safety Center database for FY 82-01. RESULTS: During FY 82-01, there were 29 G-LOC crashes while those aircraft at risk of G-LOC crashes flew a total of 13,959,816 sorties. Poisson regression showed a non-significant decrease in crashes with an incidence rate ratio (IRR) of 0.096 (CI 0.89-1.03) (4% per yr). G-LOC crashes decreased from 4.4 per million flight sorties (PMFS) to 1.6 after the implementation of anti-G-LOC training programs beginning in 1985. However, G-LOC crashes remained unchanged after implementation of PBG in 1995. In contrast, incidents showed an IRR of 1.04 (CI 1.02-1.06) for G-LOC incidents, an estimated increase of 5% per yr. DISCUSSION: The physical/mechanical limitations of PBG, risk homeostasis, and the possibility that G-LOC rates have reached their asymptotic minimum are all discussed as possible explanations for the failure of PBG to decrease G-LOC crashes.

Analysis of mission and aircraft factors in G-induced loss of consciousness in the USAF: 1982-2002.

INTRODUCTION: Previous studies have used questionnaires to evaluate G-LOC incident rates in different aircraft types, but no studies of G-LOC-related incident, crash, and fatality rates in different aircraft types were found in a search of the literature. METHODS: G-LOC events (including both incidents and crashes) for the fiscal years 1982 to 2002 were obtained from the USAF Safety Center. Aircraft sortie numbers were obtained for all aircraft that had a G-LOC event reported. Contingency table analysis and Chi-squared tests were used to evaluate differences in G-LOC rates. RESULTS: Overall 559 G-LOC events occurred for a rate of 25.9 per million sorties (PMS), but event rates differed by almost two orders of magnitude between aircraft categories, being highest in basic training aircraft, intermediate in single crewmember fighters, and lowest in other aircraft types (p < 0.001). The proportion of events resulting in crashes was 30% in single-crewmember aircraft compared with 0.6% in trainers and other two-crewmember aircraft (p < 0.001). All of the crashes and fatalities occurred in aircraft occupied at the time by only a single crewmember. The crash fatality rate was 100% in attack aircraft, 73% in single-crewmember fighters, and zero in basic trainers (p < 0.05). The F-15 and F-16 aircraft did not have higher G-LOC rates than other single-seat fighters. DISCUSSION: The data suggest that both crew complement and mission play a role in determining G-LOC rates. The data also suggest that G-LOC in an aircraft with a ground attack mission is more likely to result in a fatality.

Comparison of two sources of U.S. Air Force injury mortality data.

Is the military's casualty (mortality) reporting system a reliable surrogate for International Classification of Diseases-coded death certificate information? To answer this question, the investigators compare official casualty data to the Air Force Mortality Registry for injury-related deaths occurring in 1991-1997. The investigators first derived International Classification of Diseases, Ninth Revision and Supplementary Classification of External Causes of Injury and Poisoning (E) codes for each death from casualty data and then compared the precision of those codes with the registry's E codes derived and medically coded from death certificates and autopsy reports. Sixty-five percent of registry E codes were "precise" vs. 35% from casualty data. The registry listed nonspecific E codes for 1% (12 deaths) vs. 6% (81 deaths) for casualty data. Unlike casualty data, the registry included expectant deaths that occurred within 120 days after medical retirement. The study concludes that casualty information compares poorly with that of the registry. Air Force Mortality Registry data should be used instead of casualty data for epidemiological research.

Using safety data to describe common injury-producing events examples from the U.S. Air force.

BACKGROUND: The U.S. military leadership has recently increased its efforts to reduce the number of lost-workday injuries for both the active duty and civilian employee components of the total force. The detailed causes and circumstances of those nonfatal injuries-information needed for injury prevention-has largely been unexplored. The purpose of this project was to determine the utility of Air Force safety data for nonfatal injury prevention. METHODS: In 2004, events associated with injury-producing mishaps reported through the U.S. Air Force (USAF) Ground Safety Automated System from 1993-2002 (n = 32,812 injuries) were reconstructed. Essential data elements necessary to reconstruct event causes and circumstances were identified in both coded data and in free-text mishap narratives. Activities and mechanisms were coded in a format similar to that of the ICD-10. A taxonomy was then developed to identify hazard scenarios associated with injury-producing activities or mechanisms. RESULTS: Coded data provided only four data elements (activity, injury event/exposure, nature of injury/body part, and outcome) that were sufficiently descriptive for prevention purposes. Therefore, narrative information was coded and analyzed to obtain additional information. The assembled data enabled identification and description of hazard scenarios associated with the most common injury-producing activities and mechanisms. CONCLUSIONS: Safety reports from the USAF provide detailed mishap descriptions for lost-workday injuries that could support in-depth analysis and more effective preventive efforts. However, some of the most valuable information is found in the pre-text narratives that require coding and classification, such as was conducted for this report in order to be optimally useful for injury epidemiology and prevention.

Mechanisms of basketball injuries reported to the HQ Air Force Safety Center a 10-year descriptive study, 1993-2002.

BACKGROUND: Basketball is the most popular sport among the U.S. Air Force (USAF) active duty population and causes a large number of lost-workday injuries. The purpose of this study is to describe how basketball injuries occur to allow development of effective countermeasures. METHODS: This study used data derived from safety reports obtained from the USAF Ground Safety Automated System. Basketball injuries for the years 1993-2002 that resulted in at least one lost workday were included in the study conducted in 2003. Narrative data from 32,818 safety reports were systematically reviewed and coded in order to categorize and summarize mechanisms associated with these injuries. RESULTS: A total of 2204 mishap reports involving active duty USAF members playing basketball were documented by the study. This study identified seven mechanisms causing basketball injury. Two similar causes involving jumping (landing awkwardly and landing on someone's foot) accounted for 43% of basketball injuries followed by collisions with other players (10%). CONCLUSIONS: This study shows that mechanisms of basketball-related injury can be identified using the detailed information found in USAF safety reports. Knowledge of leading hazards or mechanisms for basketball injuries can be used to prioritize and develop prevention strategies.

Injuries to air force personnel associated with lifting, handling, and carrying objects.

BACKGROUND: The U.S. Air Force (USAF) active duty and civilian populations experience a substantial number of lost-workday injuries while lifting, handling, and carrying objects. Back injuries are most frequently reported. PURPOSE: The purpose of this study is to describe the hazard scenarios of lift-handle-carry injuries to better identify effective countermeasures. METHODS: The data were derived from safety reports obtained from the USAF Ground Safety Automated System. Lift-handle-carry injuries for the years 1993-2002 that resulted in at least one lost workday were included in the study. A total of 4085 lost-workday injuries resulting in 24,940 lost workdays for USAF military and civilian members met the criteria for inclusion. Objects associated with these injuries were identified and aggregated to determine the most common causes of lift-handle-carry injuries. RESULTS: Twelve distinct objects or type of objects were identified as the most common source of lift-handle-carry injuries. Among the most common sources of injury were lifting aircraft components, boxes, and furniture. Most importantly, lifting one group of objects, aircraft components, was associated with 33% of all lift-handle-carry injuries. CONCLUSIONS: Safety report data can be used to identify the most common object or object types causing lift-handle-carry injuries. The information included in this report suggests countermeasures that should be considered for implementation and evaluation studies. Countermeasures to address the most common lift-handle-carry injuries, such as lifting aircraft components among aircraft maintenance workers, are warranted.

A hospital-based case control study of aplastic anemia in Shanghai, China.

We report results of a hospital-based case control study of 137 consecutive patients diagnosed with aplastic anemia (AA) in participating hospitals over a 4-year period. Diagnoses were made by a single laboratory, subjects were age- and gender-matched to two controls and interviewed concerning previous disease, work histories and exposures to potential etiologic agents. Analysis was conducted on two distinct subgroups: severe aplastic anemia (SAA) and moderate aplastic anemia (MAA). In univariate regression models, the strongest associations were observed for exposure to benzene and SAA (OR=3.12, 95% CI=1.12-8.65) and life on a farm and MAA (OR=3.08, 95% CI=1.44-6.56). Benzene exposure did not show a strong dose-response relationship with either subtype. When accounting for all of the potential confounders we considered in conditional regression models, the previous relationships persisted. Other explanatory variables included hair-dye use for MAA and farm exposures, such as livestock for SAA, although most of these additional variables fell just short of statistical significance. Adjusted R-squared values were only 10% for each subtype, leaving 90% of AA occurrence unexplained. Our results suggest that: (a) benzene exposure is more strongly related to SAA than MAA, (b) farm and livestock exposures are related to both forms of AA, confirming some previous results, and (c) a large percentage of AA remains unexplained, which may indicate that individual susceptibility has a major influence on AA occurrence.

Mechanisms of slow-pitch softball injuries reported to the HQ Air Force Safety Center a 10-year descriptive study, 1993-2002.

BACKGROUND: Softball is a popular sport in civilian and military populations and results in a large number of lost-workday injuries. The purpose of this study is to describe the mechanisms associated with softball injuries occurring among active duty U.S. Air Force (USAF) personnel to better identify potentially effective countermeasures. METHODS: Data derived from safety reports were obtained from the USAF Ground Safety Automated System in 2003. Softball injuries for the years 1993-2002 that resulted in at least one lost workday were included in the study. Narrative data were systematically reviewed and coded in order to categorize and summarize mechanisms associated with these injuries. RESULTS: This report documents a total of 1181 softball-related mishap reports, involving 1171 active duty USAF members who sustained one lost-workday injury while playing softball. Eight independent mechanisms were identified. Three specific scenarios (sliding, being hit by a ball, and colliding with a player) accounted for 60% of reported softball injuries. CONCLUSIONS: Mechanisms of injury for activities such as playing softball, necessary for prevention planning, can be identified using the detailed information found in safety reports. This information should also be used to develop better sports injury coding systems. Within the USAF and U.S. softball community, interventions to reduce injuries related to the most common mechanisms (sliding, being hit by a ball, and colliding with a player) should be developed, implemented, and evaluated.

Mechanisms of flag-football injuries reported to the HQ Air Force Safety Center a 10-year descriptive study, 1993-2002.

BACKGROUND: Flag (touch or intramural) football is a popular sport among the U.S. Air Force (USAF) active duty population and causes a substantial number of lost-workday injuries. The purpose of this study is to describe the mechanisms of flag-football injuries to better identify effective countermeasures. METHODS: The data were derived from safety reports obtained from the USAF Ground Safety Automated System. Flag-football injuries for the years 1993-2002 that resulted in at least one lost workday were included in the study conducted in 2003. Narrative data were systematically reviewed for 32,812 USAF mishap reports; these were then coded in order to categorize and summarize mechanisms associated with flag football and other sports and occupational injuries. RESULTS: Nine hundred and forty-four mishap reports involving active duty USAF members playing flag football met the criteria for inclusion into this study. Eight mechanisms of injury were identified. The eight mechanisms accounted for 90% of all flag-football injuries. One scenario (contact with another player) accounted for 42% of all flag-football injuries. CONCLUSIONS: The most common mechanisms of injury caused by playing flag football can be identified using the detailed information found in safety reports. These scenarios are essential to developing evidence-based countermeasures. Results for flag football suggest that interventions that prevent player contact injuries deserve further research and evaluation. The broader implications of this study are that military safety data can be used to identify potentially modifiable mechanisms of injury for specific activities such as flag football.