Dynamics of severe accidents in the oil & gas energy sector derived from the authoritative ENergy-related severe accident database.

Organized into a global network of critical infrastructures, the oil & gas industry remains to this day the main energy contributor to the world's economy. Severe accidents occasionally occur resulting in fatalities and disruption. We build an oil & gas accident graph based on more than a thousand severe accidents for the period 1970-2016 recorded for refineries, tankers, and gas networks in the authoritative ENergy-related Severe Accident Database (ENSAD). We explore the distribution of potential chains-of-events leading to severe accidents by combining graph theory, Markov analysis and catastrophe dynamics. Using centrality measures, we first verify that human error is consistently the main source of accidents and that explosion, fire, toxic release, and element rupture are the principal sinks, but also the main catalysts for accident amplification. Second, we quantify the space of possible chains-of-events using the concept of fundamental matrix and rank them by defining a likelihood-based importance measure γ. We find that chains of up to five events can play a significant role in severe accidents, consisting of feedback loops of the aforementioned events but also of secondary events not directly identifiable from graph topology and yet participating in the most likely chains-of-events.

An Occupational Legacy: Malignant Mesothelioma Incidence and Mortality in Wisconsin.

OBJECTIVES: The aim of the study was to describe mesothelioma occurrence in Wisconsin from 1997 to 2013 by usual industry and occupation (I&O), including occupations generally considered low risk. METHODS: Population-based rates and standardized incidence and mortality ratios were calculated. Two case-control analyses were designed to compare mesothelioma incidence and mortality in specific I&O groups with occurrence of (1) brain and central nervous system cancers and (2) other causes of death, using logistic regression. RESULTS: Mesothelioma incidence and mortality were elevated in Wisconsin (SIRadj = 1.20 [1.13 to 1.28]; SMRadj = 1.30 [1.22 to 1.38]). Certain industry (construction, manufacturing) and occupation (construction and extraction) groups were associated with increased odds of mesothelioma, with some evidence of increased risk among teachers. CONCLUSIONS: Forty years after the Occupational and Safety Health Act, mesothelioma incidence and mortality remain elevated in Wisconsin, with increased risk continuing for certain I&O groups.

Associations between occupational stress and demographic characteristics in petroleum workers in the Xinjiang arid desert.

Owing to the transformation of the biomedical model of health, more and more professionals pay close attention to the occupational social psychological factors, such as occupational stress. Due to the socioeconomic impact of occupational stress and the petroleum workers stationed in the unique environment in Xinjiang, a cross-sectional study was carried out between May and December 2016 to investigate the relationship between occupational stress and demographic characteristics. A total of 1480 workers were selected. Occupational stress was evaluated with the Occupational Stress Inventory-Revised Edition. The findings of the present study revealed that the values of the Occupational Roles Questionnaire results (t = 9.266, P < .001) and Personal Strain Questionnaire results (t = 21.381, P < .001) were found to be higher than the national normal. Personal Resources Questionnaire values (t = -17.575, P < .001) were found to be lower than the national normal in petroleum workers stationed in the arid desert, and suggested a strong correlation between occupational stress and demographic characteristics. These data provide evidence that different demographic characteristics are associated with different occupational stress levels in petroleum workers stationed in the arid desert.

Risk of Lung Cancer Mortality in Nuclear Workers from Internal Exposure to Alpha Particle-emitting Radionuclides.

BACKGROUND: Carcinogenic risks of internal exposures to alpha-emitters (except radon) are poorly understood. Since exposure to alpha particles-particularly through inhalation-occurs in a range of settings, understanding consequent risks is a public health priority. We aimed to quantify dose-response relationships between lung dose from alpha-emitters and lung cancer in nuclear workers. METHODS: We conducted a case-control study, nested within Belgian, French, and UK cohorts of uranium and plutonium workers. Cases were workers who died from lung cancer; one to three controls were matched to each. Lung doses from alpha-emitters were assessed using bioassay data. We estimated excess odds ratio (OR) of lung cancer per gray (Gy) of lung dose. RESULTS: The study comprised 553 cases and 1,333 controls. Median positive total alpha lung dose was 2.42 mGy (mean: 8.13 mGy; maximum: 316 mGy); for plutonium the median was 1.27 mGy and for uranium 2.17 mGy. Excess OR/Gy (90% confidence interval)-adjusted for external radiation, socioeconomic status, and smoking-was 11 (2.6, 24) for total alpha dose, 50 (17, 106) for plutonium, and 5.3 (-1.9, 18) for uranium. CONCLUSIONS: We found strong evidence for associations between low doses from alpha-emitters and lung cancer risk. The excess OR/Gy was greater for plutonium than uranium, though confidence intervals overlap. Risk estimates were similar to those estimated previously in plutonium workers, and in uranium miners exposed to radon and its progeny. Expressed as risk/equivalent dose in sieverts (Sv), our estimates are somewhat larger than but consistent with those for atomic bomb survivors.See video abstract at, http://links.lww.com/EDE/B232.

Occupational Fatalities Resulting from Falls in the Oil and Gas Extraction Industry, United States, 2005-2014.

During 2003-2013, fatality rates for oil and gas extraction workers decreased for all causes of death except those associated with fall events, which increased 2% annually during 2003-2013 (1). To better understand risk factors for these events, CDC examined fatal fall events in the oil and gas extraction industry during 2005-2014 using data from case investigations conducted by the Occupational Safety and Health Administration (OSHA). Sixty-three fatal falls were identified, accounting for 15% of all fatal events. Among fatal falls, 33 (52%) workers fell from a height of >30 feet (9 meters), and 22 (35%) fell from the derrick board, the elevated work platform located in the derrick (structure used to support machinery on a drilling rig). Fall fatalities occurred most frequently when drilling rigs were being assembled or disassembled at the well site (rigging up or rigging down) (14; 22%) or when workers were removing or inserting drill pipe into the wellbore (14; 22%). Measures that target derrickmen and workers engaged in assembling and disassembling drilling rigs (rigging up and down) could reduce falls in this industry. Companies should annually update their fall protection plans and ensure effective fall prevention programs are in place for workers at highest risk for falls, including providing trainings on proper use, fit, and inspection of personal protective equipment.

Shale gas development and cancer incidence in southwest Pennsylvania.

OBJECTIVE: To what extent does unconventional gas development lead to an increase in cancer incidence in heavily drilled Southwest Pennsylvania? STUDY DESIGN: Ecological study. METHODS: Data for urinary bladder, thyroid and leukaemia were abstracted from the Pennsylvania Cancer Registry (PCR). Cancer incidence among counties with high, moderate and minimal number of producing wells is compared before drilling activity and thereafter. Observed vs expected cases, standardized incidence ratio and 95% confidence intervals are presented. Data are presented by county, diagnosis and sex for the years 2000-2004, 2004-2008 and 2008-2012. The percent difference between the observed cases from 2000 to 2004 and 2008-2012 was calculated. RESULTS: The observed number of urinary bladder cases was higher than expected in both sexes in counties with shale gas activity. In counties with the fewest number of producing wells, the increase was essentially non-existent. The number of observed cases of thyroid cancer increased substantially among both sexes over the time period in all counties regardless of the number of wells drilled. The pattern for leukaemia was mixed among males and females and among the counties regardless of the extent of shale gas development activities. CONCLUSION: Potential risk factors other than shale gas development must be taken into account to explain the higher than expected cancer cases in counties with and without shale gas wells before and during unconventional shale gas activity.

High Cigarette and Poly-Tobacco Use Among Workers in a Dusty Industry: New Jersey Quarry Workers.

OBJECTIVE: Tobacco use is high among US extraction and construction workers, who can also incur occupational dust exposure. Information on different types of tobacco use among quarry/mine workers is sparse. METHODS: During mandated training sessions, New Jersey quarry workers were surveyed about their tobacco use. Prevalence was calculated for single and multiple tobacco use by demographic and workplace characteristics; logistic regression was used to assess associations with smoking. RESULTS: Two hundred forty (97.1%) workers completed surveys. Among respondents, 41.7% [95% confidence interval (95% CI) 35.4 to 48.3] currently used any tobacco product of whom 28.1% smoked cigarettes. In multivariate analysis, positive associations with smoking included working as a contractor versus mine employee (odds ratio 2.32, 95% CI 1.01 to 5.36) and a usual job title of maintenance (odds ratio 2.02, 95% CI 0.87 to 4.94). CONCLUSION: Industry-specific information may be helpful in developing targeted tobacco-cessation programs.

[THE SUBSTANTIATION OF ACTIVITIES CONCERNING PRIMARY PREVENTION OF STROKE IN WORKING POPULATION].

The scale of Systematic Coronary Risk Evaluation (SCORE) was modified by introduction of such risk factors as sugar level, body mass index, locomotion activity to become a basis for development of special computer program to be applied in the study. The research purpose was to detect risk factors of cardio-vascular diseases in workers of oil processing enterprises during periodic medical examinations, to allocate patients on groups depending on intensity of risk factors and to provide recommendations on correction of risk factors. It is established that 36.2% of workers have risk factors of cardio-vascular diseases, 51.2% of males and 28.8% of females included. The arterial hypertension was detected in 28%, extra body mass and obesity in 63.6%, increased cholesterol level in 36.2%, increased sugar level of capillary blood in 42.3%, lower locomotion activity in 54.4% and tobacco smoking in 21.4% of examined patients. The most prevalent risk factors of cardio-vascular diseases among males and females turned out increased body mass, lower locomotion activity and hypercholesterolemia. The allocation of patients on groups depending on intensity of risk factors demonstrated that lower and medium risk of development of cardio-vascular diseases as present in 19.1% of examined patients, 26.1% of males and 17.9% of females included. The higher risk of development of cardio-vascular diseases was detected in 9.1% of examined patients, 13.2% of males and 8.1% of females included. The very high risk of cardio-vascular diseases was established in 8% of examined patients, 11.8% of males and 2.8% of females included. The patients of each group the individual recommendations concerning correction of risk factors were given. The developed original computer program can be applied in ambulatory polyclinic medical organizations during physician's appointment that will permit the detect group of patients with risk of development of cardio-vascular diseases. The program also gives to patients an opportunity to independently answer the questions and to receive right away recommendations concerning correction of risk factors.

Occupational fatalities during the oil and gas boom--United States, 2003-2013.

During 2003-2013, the U.S. oil and gas extraction industry experienced unprecedented growth, doubling the size of its workforce and increasing the number of drilling rigs by 71%. To describe fatal events among oil and gas workers during this period, CDC analyzed data from the Bureau of Labor Statistics (BLS) Census of Fatal Occupational Injuries (CFOI), a comprehensive database of fatal work injuries. During 2003-2013, the number of work-related fatalities in the oil and gas extraction industry increased 27.6%, with a total of 1,189 deaths; however, the annual occupational fatality rate significantly decreased 36.3% (p<0.05) during this 11-year period. Two-thirds of all worker fatalities were attributed to transportation incidents (479, [40.3%]) and contact with objects/equipment (308 [25.9%]). More than 50% of persons fatally injured were employed by companies that service wells (615 [51.7%]). It is important for employers to consider measures such as land transportation safety policies and engineering controls (e.g., automated technologies) that would address these leading causes of death and reduce workers' exposure to hazards.

Measurements of methane emissions from natural gas gathering facilities and processing plants: measurement results.

Facility-level methane emissions were measured at 114 gathering facilities and 16 processing plants in the United States natural gas system. At gathering facilities, the measured methane emission rates ranged from 0.7 to 700 kg per hour (kg/h) (0.6 to 600 standard cubic feet per minute (scfm)). Normalized emissions (as a % of total methane throughput) were less than 1% for 85 gathering facilities and 19 had normalized emissions less than 0.1%. The range of methane emissions rates for processing plants was 3 to 600 kg/h (3 to 524 scfm), corresponding to normalized methane emissions rates <1% in all cases. The distributions of methane emissions, particularly for gathering facilities, are skewed. For example, 30% of gathering facilities contribute 80% of the total emissions. Normalized emissions rates are negatively correlated with facility throughput. The variation in methane emissions also appears driven by differences between inlet and outlet pressure, as well as venting and leaking equipment. Substantial venting from liquids storage tanks was observed at 20% of gathering facilities. Emissions rates at these facilities were, on average, around four times the rates observed at similar facilities without substantial venting.

Interleukin-10 involvement in exposure to low dose of benzene.

OBJECTIVE: To establish if serum levels of interleukin-10 (IL-10) in subjects exposed to benzene are connected with age, working years, and employment age. METHODS: We evaluated serum levels of IL-10 in 51 employees working in oil refinery (group A) and in 16 office workers who resided in the same area (group B). RESULTS: There was no statistically significant difference between serum concentrations of IL-10 in groups A and B. There was a statistically significant dependent relationship in group A between age, working years, and serum concentration of IL-10. There was a statistically significant and positive dependent relationship in group A between serum concentration of IL-10 and employment age. CONCLUSIONS: The role played by IL-10 in benzene immune suppression may be relevant and attention should be directed toward assessment of age, working years, and employment age in benzene-exposed populations.

Injury rates on new and old technology oil and gas rigs operated by the largest United States onshore drilling contractor.

BACKGROUND: Occupational fatality rates among oil and gas extraction industry and specifically among drilling contractor workers are high compared to the U.S. all-industry average. There is scant literature focused on non-fatal injuries among drilling contractors, some of which have introduced engineering controls to improve rig efficiency and reduce injury risk. METHODS: We compared injury rates on new and old technology rigs operated by the largest U.S. drilling contractor during 2003-2012, stratifying by job type and grouping outcomes by injury severity and body part affected. RESULTS: Six hundred seventy-one injuries were recorded over 77.4 million person-hours. The rate on new rigs was 66% of that on old rigs. Roughnecks had lower injury rates on new rigs, largely through reduced limb injury rates. New rigs had lower rates in each non-fatal injury severity category. CONCLUSIONS: For this company, new technology rigs appear to provide a safer environment for roughnecks. Future studies could include data from additional companies.

[Risk factors for absenteeism due to sick leave in the petroleum industry]. / Fatores de risco para absenteísmo com licença médica em trabalhadores da indústria de petróleo.

OBJECTIVE: To identify risk factors for absenteeism among workers with sick leave in an oil company. METHODS: A case-control study (120 cases and 656 controls) nested in a retrospective cohort study following up all employees of an oil company in the North-Northeast of Brazil from 2007 to 2009. The response variable used to represent absenteeism with sick leave was the average incidence of sick leave, defined as the ratio between total sick days and potential working days in the period. Logistic regression techniques were used to investigate the association between average incidence of sick leave > 5.0% over the period and the variables sex, position, age, time at work, shift work, smoking, arterial hypertension, body mass index, physical activity, coronary risk, sleep, glycemia, non-managed diabetes, cardiovascular, digestive, musculoskeletal, neurological and neoplastic diseases, straining body positioning during work, satisfaction at work, relationship with management, and concentrated attention at work. RESULTS: Average incidence of sick leave higher than 5.0% in the cohort period was 15.5%. The logistic model revealed that workers with average incidence of sick leave higher than 5.0% were 2.6 times more likely to be female; 2.0 time more likely to be smokers; 1.8 time more likely to be former smokers; 2.2 times more likely to report abnormal sleep and 10.5 times more likely to report dissatisfaction with their than workers with average incidence of sick leave ≤ 5.0% in the period. CONCLUSIONS: In this population, female gender, being a smoker or a former smoker, reporting dissatisfaction with the job and reporting abnormal sleep are good predictors of occupational absenteeism with sick leave. OBJECTIVE: To identify risk factors for absenteeism among workers with sick leave in an oil company. METHODS: A case-control study (120 cases and 656 controls) nested in a retrospective cohort study following up all employees of an oil company in the North-Northeast of Brazil from 2007 to 2009. The response variable used to represent absenteeism with sick leave was the average incidence of sick leave, defined as the ratio between total sick days and potential working days in the period. Logistic regression techniques were used to investigate the association between average incidence of sick leave > 5.0% over the period and the variables sex, position, age, time at work, shift work, smoking, arterial hypertension, body mass index, physical activity, coronary risk, sleep, glycemia, non-managed diabetes, cardiovascular, digestive, musculoskeletal, neurological and neoplastic diseases, straining body positioning during work, satisfaction at work, relationship with management, and concentrated attention at work. RESULTS: Average incidence of sick leave higher than 5.0% in the cohort period was 15.5%. The logistic model revealed that workers with average incidence of sick leave higher than 5.0% were 2.6 times more likely to be female; 2.0 time more likely to be smokers; 1.8 time more likely to be former smokers; 2.2 times more likely to report abnormal sleep and 10.5 times more likely to report dissatisfaction with their than workers with average incidence of sick leave ≤ 5.0% in the period. CONCLUSIONS: In this population, female gender, being a smoker or a former smoker, reporting dissatisfaction with the job and reporting abnormal sleep are good predictors of occupational absenteeism with sick leave.

Evaluating officially reported polycyclic aromatic hydrocarbon emissions in the Athabasca oil sands region with a multimedia fate model.

Emissions of organic substances with potential toxicity to humans and the environment are a major concern surrounding the rapid industrial development in the Athabasca oil sands region (AOSR). Although concentrations of polycyclic aromatic hydrocarbons (PAHs) in some environmental samples have been reported, a comprehensive picture of organic contaminant sources, pathways, and sinks within the AOSR has yet to be elucidated. We sought to use a dynamic multimedia environmental fate model to reconcile the emissions and residue levels reported for three representative PAHs in the AOSR. Data describing emissions to air compiled from two official sources result in simulated concentrations in air, soil, water, and foliage that tend to fall close to or below the minimum measured concentrations of phenanthrene, pyrene, and benzo(a)pyrene in the environment. Accounting for evaporative emissions (e.g., from tailings pond disposal) provides a more realistic representation of PAH distribution in the AOSR. Such indirect emissions to air were found to be a greater contributor of PAHs to the AOSR atmosphere relative to reported direct emissions to air. The indirect pathway transporting uncontrolled releases of PAHs to aquatic systems via the atmosphere may be as significant a contributor of PAHs to aquatic systems as other supply pathways. Emission density estimates for the three PAHs that account for tailings pond disposal are much closer to estimated global averages than estimates based on the available emissions datasets, which fall close to the global minima. Our results highlight the need for improved accounting of PAH emissions from oil sands operations, especially in light of continued expansion of these operations.

Evaluation of impact of shale gas operations in the Barnett Shale region on volatile organic compounds in air and potential human health risks.

Shale gas exploration and production (E&P) has experienced substantial growth across the U.S. over the last decade. The Barnett Shale, in north-central Texas, contains one of the largest, most active onshore gas fields in North America, stretching across 5000 square miles and having an estimated 15,870 producing wells as of 2011. Given that these operations may occur in relatively close proximity to populated/urban areas, concerns have been expressed about potential impacts on human health. In response to these concerns, the Texas Commission on Environmental Quality established an extensive air monitoring network in the region. This network provides a unique data set for evaluating the potential impact of shale gas E&P activities on human health. As such, the objective of this study was to evaluate community-wide exposures to volatile organic compounds (VOCs) in the Barnett Shale region. In this current study, more than 4.6 million data points (representing data from seven monitors at six locations, up to 105 VOCs/monitor, and periods of record dating back to 2000) were evaluated. Measured air concentrations were compared to federal and state health-based air comparison values (HBACVs) to assess potential acute and chronic health effects. None of the measured VOC concentrations exceeded applicable acute HBACVs. Only one chemical (1,2-dibromoethane) exceeded its applicable chronic HBACV, but it is not known to be associated with shale gas production activities. Annual average concentrations were also evaluated in deterministic and probabilistic risk assessments and all risks/hazards were below levels of concern. The analyses demonstrate that, for the extensive number of VOCs measured, shale gas production activities have not resulted in community-wide exposures to those VOCs at levels that would pose a health concern. With the high density of active wells in this region, these findings may be useful for understanding potential health risks in other shale play regions.

Fatores de risco para absenteísmo com licença médica em trabalhadores da indústria de petróleo / Risk factors for absenteeism due to sick leave in the petroleum industry / Risk factors for absenteeism due to sick leave in the petroleum industryFactores de riesgo para el ausentismo con licencia médica en trabajadores de la industria del petróleo / Factores de riesgo para el ausentismo con licencia médica en trabajadores de la industria del petróleo

OBJETIVO : Identificar fatores de risco para o absenteísmo com licença médica em trabalhadores de empresa de petróleo. MÉTODOS : Estudo caso-controle (120 casos e 656 controles) aninhado a um estudo de coorte retrospectivo com todos os trabalhadores de uma empresa de petróleo na Região Norte-Nordeste do Brasil entre 2007 e 2009. A variável resposta utilizada para representar o absenteísmo com licença médica foi a incidência média de faltas com licenças médicas no período, definida pela razão entre o total de dias de licenças médicas e os dias potencialmente trabalháveis no período. Análise de regressão logística foi utilizada para investigar a associação entre incidência média de faltas > 5,0% no período e as variáveis sexo, cargo, idade, tempo de atuação, regime de trabalho, tabagismo, hipertensão arterial, índice de massa corporal, atividade física, risco coronariano, sono, glicemia, diabetes não controlado, doença do aparelho cardiovascular, digestivo, aparelho locomotor, neurológica, neoplasia, posturas forçadas no trabalho, satisfação com o trabalho, relacionamento com a chefia e atenção concentrada no trabalho. RESULTADOS : A incidência média de faltas com licenças médicas > 5,0% no período da coorte foi 15,5%. O modelo logístico revelou que trabalhadores com incidência média de faltas > 5,0% tiveram 2,6 vezes mais chance de ser do sexo feminino; 2,0 vezes mais chance de ser fumante; 1,8 vez mais chance de ser ex-fumante, 2,2 vezes mais chance de relatar sono anormal e 10,5 vezes mais chance de estarem insatisfeitos com o trabalho do que trabalhadores com incidência média de faltas ≤ 5,0% no período. CONCLUSÕES : Sexo feminino, ser fumante ...

OBJECTIVE : To identify risk factors for absenteeism among workers with sick leave in an oil company. METHODS : A case-control study (120 cases and 656 controls) nested in a retrospective cohort study following up all employees of an oil company in the North-Northeast of Brazil from 2007 to 2009. The response variable used to represent absenteeism with sick leave was the average incidence of sick leave, defined as the ratio between total sick days and potential working days in the period. Logistic regression techniques were used to investigate the association between average incidence of sick leave > 5.0% over the period and the variables sex, position, age, time at work, shift work, smoking, arterial hypertension, body mass index, physical activity, coronary risk, sleep, glycemia, non-managed diabetes, cardiovascular, digestive, musculoskeletal, neurological and neoplastic diseases, straining body positioning during work, satisfaction at work, relationship with management, and concentrated attention at work. RESULTS : Average incidence of sick leave higher than 5.0% in the cohort period was 15.5%. The logistic model revealed that workers with average incidence of sick leave higher than 5.0% were 2.6 times more likely to be female; 2.0 time more likely to be smokers; 1.8 time more likely to be former smokers; 2.2 times more likely to report abnormal sleep and 10.5 times more likely to report dissatisfaction with their than workers with average incidence of sick leave ≤ 5.0% in the period. CONCLUSIONS : In this population, female gender, being a smoker or a former smoker, reporting dissatisfaction with the job and reporting abnormal sleep are good predictors of occupational absenteeism with sick leave. .

OBJECTIVE : To identify risk factors for absenteeism among workers with sick leave in an oil company. METHODS : A case-control study (120 cases and 656 controls) nested in a retrospective cohort study following up all employees of an oil company in the North-Northeast of Brazil from 2007 to 2009. The response variable used to represent absenteeism with sick leave was the average incidence of sick leave, defined as the ratio between total sick days and potential working days in the period. Logistic regression techniques were used to investigate the association between average incidence of sick leave > 5.0% over the period and the variables sex, position, age, time at work, shift work, smoking, arterial hypertension, body mass index, physical activity, coronary risk, sleep, glycemia, non-managed diabetes, cardiovascular, digestive, musculoskeletal, neurological and neoplastic diseases, straining body positioning during work, satisfaction at work, relationship with management, and concentrated attention at work. RESULTS : Average incidence of sick leave higher than 5.0% in the cohort period was 15.5%. The logistic model revealed that workers with average incidence of sick leave higher than 5.0% were 2.6 times more likely to be female; 2.0 time more likely to be smokers; 1.8 time more likely to be former smokers; 2.2 times more likely to report abnormal sleep and 10.5 times more likely to report dissatisfaction with their than workers with average incidence of sick leave ≤ 5.0% in the period. CONCLUSIONS : In this population, female gender, being a smoker or a former smoker, reporting dissatisfaction with the job and reporting abnormal sleep are good predictors of occupational absenteeism with sick leave. .

OBJETIVO : Identificar factores de riesgo para el ausentismo con licencia médica en trabajadores de empresa del petróleo. MÉTODOS : Estudio caso-control (120 casos y 656 controles) anidado en una cohorte retrospectiva con todos los trabajadores de una empresa de petróleo en la Región Norte-Nordeste de Brasil entre 2007 y 2009. La variable respuesta utilizada para representar el ausentismo con licencia médica fue la incidencia promedio de faltas con licencias médicas durante el período, definida por el cociente entre el total de días de licencias médicas y los días potencialmente trabajables. Se utilizó análisis de regresión logística para investigar la asociación entre incidencia promedio de faltas > 5,0% en el período y las variables sexo, cargo, edad, tiempo de actuación, régimen de trabajo, tabaquismo, hipertensión arterial, índice de masa corporal, actividad física, riesgo coronario, sueño, glicemia, diabetes no controlada, enfermedad del aparato cardiovascular, digestivo, aparato locomotor, neurológica, neoplasia, posturas forzadas en el trabajo, satisfacción con el trabajo, relacionamiento con el jefe y atención concentrada en el trabajo. RESULTADOS : La incidencia promedio de faltas con licencias médicas > 5,0% en el período de la cohorte fue de 15,5%. El modelo logístico reveló que trabajadores con incidencia promedio de faltas > 5,0% tuvieron 2,6 veces más chance de ser del sexo femenino; 2,0 veces más chances de ser fumador; 1,9 veces más chance de ser ex-fumador; 2,1 veces más chance de relatar sueño anormal y 10,5 veces más chances de estar insatisfechos con el trabajo, en comparación con los trabajadores con incidencia promedio de faltas < 5,0% en el período. CONCLUSIONES : Sexo femenino, ser fumador o ex-fumador, estar ...

Gas production in the Barnett Shale obeys a simple scaling theory.

Natural gas from tight shale formations will provide the United States with a major source of energy over the next several decades. Estimates of gas production from these formations have mainly relied on formulas designed for wells with a different geometry. We consider the simplest model of gas production consistent with the basic physics and geometry of the extraction process. In principle, solutions of the model depend upon many parameters, but in practice and within a given gas field, all but two can be fixed at typical values, leading to a nonlinear diffusion problem we solve exactly with a scaling curve. The scaling curve production rate declines as 1 over the square root of time early on, and it later declines exponentially. This simple model provides a surprisingly accurate description of gas extraction from 8,294 wells in the United States' oldest shale play, the Barnett Shale. There is good agreement with the scaling theory for 2,057 horizontal wells in which production started to decline exponentially in less than 10 y. The remaining 6,237 horizontal wells in our analysis are too young for us to predict when exponential decline will set in, but the model can nevertheless be used to establish lower and upper bounds on well lifetime. Finally, we obtain upper and lower bounds on the gas that will be produced by the wells in our sample, individually and in total. The estimated ultimate recovery from our sample of 8,294 wells is between 10 and 20 trillion standard cubic feet.