Back pain in migrant farmworker families and farmworker high school students from Starr County, Texas

Back symptoms are a major global public health problem with the lifetime prevalence ranging between 50-80%. Research suggests that work-related factors contribute to the occurrence of back pain in various industries. Despite the hazardous nature, strenuous tasks, and awkward postures associated with farm work, little is known about back injury and symptoms in farmworker adults and children. Research in the United States is particularly limited. This is a concern given the large proportion of migrant farmworkers in the United States without adequate access to healthcare as well as a substantial number of youth working in agriculture. The present study describes back symptoms and identifies work-related factors associated with back pain in migrant farmworker families and farmworker high school students from Starr County, TX. Two separate datasets were used from two cohort studies "Injury and Illness Surveillance in Migrant Farmworkers (MANOS)" (study A: n=267 families) and "South Texas Adolescent Rural Research Study (STARRS)" (study B: n=345). Descriptive and inferential statistics including multivariable logistic regression were used to identify work-related factors associated with back pain in each study. In migrant farmworker families, the prevalence of chronic back pain during the last migration season ranged from 9.5% among youngest children to 33.3% among mothers. Chronic back pain was significantly associated with increasing age; fairly bad/very bad quality of sleep while migrating; fewer than eight hours of sleep at home in Starr County, TX; depressive symptoms while migrating; self-provided water for washing hands/drinking; weeding at work; and exposure to pesticide drift/direct spray. Among farmworker adolescents, the prevalence of severe back symptoms was 15.7%. Severe back symptoms were significantly associated with being female; history of a prior accident/back injury; feeling tense, stressed, or anxious sometimes/often; lifting/carrying heavy objects not at work; current tobacco use; increasing lifetime number of migrant farmworker years; working with/around knives; and working on corn crops. Overall, results support that associations between work-related exposures and chronic back pain and severe back symptoms remain after controlling for the effect of non-work exposures in farmworker populations. ^

Airliner cabin air quality exposure assessment

The airliner cabin environment and its effects on occupant health have not been fully characterized. This dissertation is: (1) A review of airliner environmental control systems (ECSs) that modulate the ventilation, temperature, relative humidity (RH), and barometric pressure (PB) of the cabin environment---variables related to occupant comfort and health. (2) A review and assessment of the methods and findings of key cabin air quality (CAQ) investigations. Several significant deficiencies impede the drawing of inferences about CAQ, e.g., lack of detail about investigative methods, differences in methods between investigations, limited assessment of CAQ variables, small sample sizes, and technological deficiencies of data collection. (3) A comprehensive evaluation of the methods used in the subsequent NIOSH-FAA Airliner CAQ Exposure Assessment Feasibility Study (STUDY) in which this author participated. A number of problems were identified which limit the usefulness of the data. (4) An analysis of the reliable 10-flight STUDY data. Univariate and multivariate methods applied to CO2 (a surrogate for air contaminants), temperature, RH, and PB, in association with percent passenger load, ventilation system, flight duration, airliner body type, and measurement location within the cabin, revealed neither the measured values nor their variability exceeded established health-based exposure limits. Regression analyses suggest CO2, temperature, and RH were affected by percent passenger load. In-flight measurements of CO2 and RH were relatively independent of ventilation system type or flight duration. Cabin temperature was associated with percent passenger load, ventilation system type, and flight duration. (5) A synthesis of the implications of the airliner ECS and cabin O2 environment on occupant health. A model was developed to predict consequences of the airliner cabin pressure altitude 8,000 ft limit and resulting model-estimated PO2 on cardiopulmonary status. Based on the PB, altitude, and environmental data derived from the 10 STUDY flights, the predicted PaO2 of adults with COPD, or elderly adults with or without COPD, breathing ambient cabin air could be < 55 mm Hg (SaO2 < 88%). Reduction in cabin PB found in the STUDY flights could aggravate various medical conditions and require the use of in-flight supplemental O2. ^

Gasoline and leukemia: A review

Gasoline is perhaps one of the most familiar substances to people in our society. Benzene is a component of gasoline and it is hemotoxic and carcinogenic at high concentrations. With increased governmental regulation of gasoline and benzene exposure, the hazardous effects of benzene on public health are very limited. As long as environmental conditions meet OSHA regulation standards, most individuals are not aware of the hazardous effect of benzene. However, recent studies have found that less than 1ppm benzene exposure which is below OSHA exposure regulatory standard may cause hematological damage. This paper reviews the relationship among gasoline-related work, daily life gasoline exposure, public health and new updated research in this field. We searched for relevant publications from 1966 through 2006 in three databases: Ovid Medline, PubMed and TOXNET. This review is a means toward educating people about exposure to benzene in different environments. Although government has developed good monitoring and prevention methods to decrease the harm from gasoline, we are aware that the problem is still there. The primary public health message is the benzene may cause hematological effects even at or below the U.S occupational standard of 1ppm.^

Lab animal allergy surveillance at a private medical school in three dissimilar animal research facilities

Very few studies have described MUP-1 concentrations and measured prevalence of Laboratory Animal Allergy (LAA) at such a diverse institution as the private medical school (MS) that is the focus of this study. Air sampling was performed in three dissimilar animal research facilities at MS and quantitated using a commercially available ELISA. Descriptive data was obtained from an anonymous laboratory animal allergy survey given to both animal facility employees and the researchers who utilize these facilities alike. Logistic regression analysis was then implemented to investigate specific factors that may be predictive of developing LAA as well as factors influencing the reporting of LAA symptoms to the occupational health program. Concentrations of MUP-1 detected ranged from below detectable levels (BDL) to a peak of 22.64 ng/m3 . Overall, 68 employees with symptoms claimed they improved while away from work and only 25 employees reported their symptoms to occupational health. Being Vietnamese, a smoker, not wearing a mask, and working in any facility longer than one year were all significant predictors of having LAA symptoms. This study suggests a LAA monitoring system that relies on self-reporting can be inadequate in estimating LAA problems. In addition, efforts need to be made to target training and educational materials for non-native English speaking employees to overcome language and cultural barriers and address their specific needs. ^

Evaluation of obesity interventions targeting adults in the occupational setting

The study of obesity and its causes has evolved into one of the most important public health issues in the United States (Office of Disease Prevention and Health Promotion, 2007). Obesity is linked to several chronic conditions, such as cardiovascular disease, diabetes and some cancers (National Center for Chronic Disease Prevention and Health Promotion, 2008b) and the public health concern resides in the present morbidity and mortality associated with obesity and related conditions (National Heart, Lung and Blood Institute, 1998). Furthermore, obesity and its related conditions present economic challenges to employers in terms of medical health care, sick leave, short-term disability and long-term disability benefits utilized by employees (Østbye, Dement, and Krause, 2007). Recently, articles covering intervention programs targeting obesity in the occupational setting have surfaced in the body of scientific literature. The increased interest in this area stems from the fact that employees in the United States spend more time in the work environment than many industrialized nations, including Japan and most of Western Europe (Organisation for Economic Co-operation and Development, 2006). Moreover, scientific literature supports the idea of investing in healthy human capital to promote productivity and output from employees (Berger, Howell, Nicholson, & Sharda, 2003). The time spent in the work environment, the business need for healthy employees, and the public health concern create an opportunity for planning, implementation and analysis of interventions for effectiveness. This paper aims to identify those intervention programs that focus on the occupational setting related to obesity, to analyze the overall effect of diet, physical fitness and behavioral change interventions targeting overweight and obesity in the occupational setting, and to evaluate the details and effectiveness of components, such as, intervention setting, target participant group, content, industry and length of follow up. Once strengths and weaknesses of the interventions are evaluated, ideas will be suggested for implementation in the future.^

The experience and meaning of injury among migrant farmworkers from Starr County, Texas

Occupational injuries suffered by migrant farmworkers in the United States continue to be a significant byproduct of the hazards of the agricultural work sector. Although the fields of study involving occupational health and safety have helped to further an understanding of the importance of injury prevention in the workplace, farmworkers have typically not been the beneficiaries of significant improvement in working conditions; similarly, public health policies have generally not been successful in significantly improving their protection. The primary objective of this research was to examine more closely, through in-depth interviews, the underlying reasons attributed by migrant farmworkers to their having suffered occupational injuries. By re-contacting and re-interviewing migrant farmworkers who had reported injuries in a study entitled A Cohort Study of Injuries in Migrant Farmworker Families in South Texas, the current research study employed qualitative research methods and determined several reasons that may help to explain why this specific group has suffered injuries and may not have reported such injuries, as well as to consider what their experiences may say about injury prevention within the context of public health.^

Implementing the Global Plan of Action on workers' health: Components to protect health care workers

Health care workers are at risk for percutaneous injuries and infection with blood born pathogens due to needle stick injuries with contaminated needles. The most common pathogens transmitted are hepatitis B, and C and HIV/AIDS. According to the WHO Global Plan of Action (GPA) a large gap exist between and within countries with regards to the health status of workers and their exposure to occupational risk. Less than 15% of the world's work forces have access to occupational health services despite the availability of effective interventions that can prevent occupational hazards, or protect and promote health in the workplace. The 2006 World Health Report declared that there is a global crisis in the health care work force. 1 in 400 of the world's health care workers work in Sub-Saharan Africa. 1 in 3 work in the U.S or Canada. The shortage of health care workers is worst in Southeast Asia and Sub-Saharan Africa. These countries have the highest burden of exposure to contaminated sharps. They rarely, if ever monitor the exposure or health impact of occupational ailments and injuries on workers. Many injuries are unreported. Occupational health services in the developing world are virtually non existent. Many health care workers leave their home countries and go to work in other countries where the working conditions, occupational services included, are better. The inability of countries to provide the necessary numbers of health care workers to provide a high level of health coverage is a threat to national and international public health security. Immunizing health care workers against hepatitis B and providing them PEP, PPE, education and safety training is an essential part of increasing and maintaining the numbers of health care workers in the critical shortage areas. ^

Disparities in asthma prevalence: The influence of sociodemographic and workplace factors

Asthma is a serious and continuing health problem that affects millions of Americans. Our study was conducted in response to this serious health problem and for purposes of addressing the issue of potential health disparities as outlined in Healthy People 2010. Data from sub-populations of subjects who participated in the National Health and Nutrition Examination Survey (NHANES) from 1999-2004 were used to complete the following specific aims: (1) to update nationally-based estimates of the prevalence of current and lifetime (ever) asthma among adults in the United States (U.S.) and describe by gender the relationships between potential risk factors (e.g., sociodemographics and lifestyle) and asthma; (2) to describe demographic characteristics among working adults in the U.S. and update estimates of the prevalence of asthma in this sub-population, stratified by occupation and industry; and 3) to determine the utility of adapting a population-based Job Exposure Matrix (JEM) for classifying workplace exposures to asthmagens. ^ Our findings suggest the prevalence of asthma among U.S. adults is continuing to rise, with women having a higher prevalence of asthma than men. Living below the poverty threshold, obesity, and prior history of smoking remain important determinants of asthma. Our study also adds to the increasing evidence that health care workers (HCWs) and those employed in education remain at high risk and that appropriate evaluation and control measures need to be implemented. Over 78% of HCWs and 71% of teachers in our study were females suggesting that further exploration of gender-specific risk factors of asthma in working populations is needed. ^ Our study also addressed the feasibility of adapting a population-based asthma-specific JEM to NHANES (1999-2004). We were not able to apply the asthma-specific JEM due to the broad occupational categories within NHANES. This represents a missed opportunity to examine the association between workplace exposures and asthma in U.S. working adults. However, we have identified steps that may be implemented in future population-based studies that would allow the asthma-specific JEM (and other population-based job exposure matrices) to be used in future studies of the U.S. working population.^

Use of light intensity, temperature, and humidity to verify exposure location

Research studies on the association between exposures to air contaminants and disease frequently use worn dosimeters to measure the concentration of the contaminant of interest. But investigation of exposure determinants requires additional knowledge beyond concentration, i.e., knowledge about personal activity such as whether the exposure occurred in a building or outdoors. Current studies frequently depend upon manual activity logging to record location. This study's purpose was to evaluate the use of a worn data logger recording three environmental parameters—temperature, humidity, and light intensity—as well as time of day, to determine indoor or outdoor location, with an ultimate aim of eliminating the need to manually log location or at least providing a method to verify such logs. For this study, data collection was limited to a single geographical area (Houston, Texas metropolitan area) during a single season (winter) using a HOBO H8 four-channel data logger. Data for development of a Location Model were collected using the logger for deliberate sampling of programmed activities in outdoor, building, and vehicle locations at various times of day. The Model was developed by analyzing the distributions of environmental parameters by location and time to establish a prioritized set of cut points for assessing locations. The final Model consisted of four "processors" that varied these priorities and cut points. Data to evaluate the Model were collected by wearing the logger during "typical days" while maintaining a location log. The Model was tested by feeding the typical day data into each processor and generating assessed locations for each record. These assessed locations were then compared with true locations recorded in the manual log to determine accurate versus erroneous assessments. The utility of each processor was evaluated by calculating overall error rates across all times of day, and calculating individual error rates by time of day. Unfortunately, the error rates were large, such that there would be no benefit in using the Model. Another analysis in which assessed locations were classified as either indoor (including both building and vehicle) or outdoor yielded slightly lower error rates that still precluded any benefit of the Model's use.^

Psychosocial factors and musculoskeletal symptoms in a vulnerable working population in Nicaragua

This research is a secondary data analysis of the CUPID-INCA Nicaragua study, a cross-sectional study comparing psychosocial and physical factors on musculoskeletal symptoms among nurses, office workers and maquiladoras in Nicaragua. There were three objectives for this thesis. (1) To describe the study population according to their socio-demographic, psychosocial (i.e. work organization and health beliefs) and physical factors. (2) To estimate the prevalence of musculoskeletal disorders (MSDs) in the study population (nurses, office workers and maquilas). (3) To analyze and compare the trends of association between psychosocial factors and MSDs to that of physical factors and MSDs in the study population. Trends of association between MSDs and psychosocial factors were also compared between nurses, office workers and maquilas. ^ Majority of the total study population were females, middle aged, non smokers and had been on the job for more than five years. Prevalence rates of low back pain and upper extremity pain were 28% and 37% respectively in nurses, 17% and 34% in office workers and 18% and 31% in maquilas. Workers' health belief was significantly associated with MSDs in all three occupational groups. Psychosocial factors were not consistently associated more with MSDs than physical factors. Maquilas had more psychosocial factors statistically significantly associated with musculoskeletal symptoms than nurses and office workers. ^ The findings of this research suggest that both psychosocial and physical risk factors play a role on the prevalence of musculoskeletal symptoms in the three working populations in Nicaragua. Future research in this area should explore further, the risk of developing MSDs from workers' exposure to psychosocial factors as well as physical factors.^

Occupation and glioma: The Harris County Brain Tumor Study, 2001--2010

The relationship between occupational exposures and glioma has not been adequately assessed due to the lack of studies in current scientific literature. To address this disparity, the Harris County Brain Tumor Study, an ongoing population-based case-control study, began in January 2001. Longest-held occupation for 382 cases and 629 controls were frequency matched on age (within 5 years), sex, and race and placed into 14 predetermined occupational categories. Adjusted odds ratios and 95% confidence intervals were calculated for each category using multiple logistic regression. Potential confounders assessed included sex, age, smoking status, education and income. For all subjects, significantly elevated adjusted odds ratios were found in health-related (aOR=1.66; 95%CI=1.03, 2.68), teaching (aOR=1.84; 95%CI=1.17, 2.88), and protective service (aOR=3.6; 95%CI=1.05, 12.31) occupational categories after controlling for sex and education. A significantly lowered odds ratio was seen in the writers, artists, and entertainers category (aOR=0.14; 95%CI=0.03, 0.58). In the stratified analyses, which controlled for education, males had a significantly elevated odds ratio for protective service workers (aOR=4.83; 95%CI=1.24, 18.83) while a significantly lower odds ratio was found in mechanics and machine operators (aOR=0.33; 95%CI=0.12,0.87). In females, we observed a significantly elevated odds ratio in teachers (aOR=1.99; 95%CI=1.20,3.31) and a significantly lower odds ratio in clerical workers (aOR=0.63; 95%CI=0.45,0.90). These analyses revealed several significant associations and allowed for separate analyses by gender, distinguishing this study from many glioma studies. Further analyses should provide a large enough sample size to stratify by gender as well as histological subtype.^

Assessment of occupational exposures to organic chemicals in a plastics manufacturing facility

The objective of this dissertation was to design and implement strategies for assessment of exposures to organic chemicals used in the production of a styrene-butadiene polymer at the Texas Plastics Company (TPC). Linear statistical retrospective exposure models, univariate and multivariate, were developed based on the validation of historical industrial hygiene monitoring data collected by industrial hygienists at TPC, and additional current industrial hygiene monitoring data collected for the purposes of this study. The current monitoring data served several purposes. First, it provided information on current exposure data, in the form of unbiased estimates of mean exposure to organic chemicals for each job title included. Second, it provided information on homogeneity of exposure within each job title, through the use of a carefully designed sampling scheme which addressed variability of exposure both between and within job titles. Third, it permitted the investigation of how well current exposure data can serve as an evaluation tool for retrospective exposure estimation. Finally, this dissertation investigated the simultaneous evaluation of exposure to several chemicals, as well as the use of values below detection limits in a multivariate linear statistical model of exposures. ^

The origin and development of hyperammonemia following exposure to hydrazine in rabbits

Hydrazine $\rm (N\sb2H\sb4),$ an important liquid propellant and derivative chemical for pharmaceuticals and pesticides, produces coma and convulsions sometimes resulting in death. Hyperammonia was found in rabbits exposed to 18 mg/Kg of hydrazine. Results of Part One of this study of rabbits emphasize the importance of acute ammonia toxicity during the first three hours following exposure to hydrazine. At no time during this post exposure period did a significant reduction of hydrazine to ammonia occur. Therefore, the elevated blood ammonia was apparently secondary to the effects of hydrazine on metabolic pathways. Further, the results support the theory of competitive inhibition of ammonia by hydrazine and emphasize the need to monitor plasma ammonia following toxic exposure to hydrazine.^ In Part Two, urea, ammonia, CO$\sb2,$ pH, glucose, sodium, potassium, chloride and creatinine were measured for up to 4 hours following injection of 18 mg/Kg of hydrazine in each of two groups of five rabbits. One group received normal saline and the other group received 5% dextrose and water/normal saline. Hyperammonemia, minimal metabolic acidosis and hyperglycemia without increased urea were found in the rabbits receiving normal saline intravenous infusion and hydrazine injection. Hence, hypoglycemia does not appear to play a role in the development of hyperammonemia. A significant difference in the elevated ammonia levels between the two groups receiving dextrose and water/normal saline and normal saline at 1 hour occurred. There was no significant difference in the elevated ammonia levels seen between the two groups receiving dextrose and water/normal saline and normal saline at 2.5 and 4 hours. Thus at 1 hour the group receiving dextrose was able to utilize excess glucose to detoxify ammonia, while at 2.5 and 4 hours there was no significant difference in the two groups' ability to detoxify ammonia.^ Findings support the theory that hydrazine inhibits the formation of urea resulting in hyperammonemia. Results suggest that hydrazine at 18 mg/Kg, a known hypoglycemic agent, causes serious hyperammonemia without increasing urea production during hyperglycemia. These experiments support a unified theory for the toxic mechanism of action of hydrazine, i.e., the intermediary metabolic effects of hydrazine are brought about by the formation of hydrazones which encumber ATP synthesis and vitamin B$\sb6$ enzymatic reactions. ^

A nested case-control study of radiation exposure and brain cancer incidence in the United States Air Force

A nested case-control study design was used to investigate the relationship between radiation exposure and brain cancer risk in the United States Air Force (USAF). The cohort consisted of approximately 880,000 men with at least 1 year of service between 1970 and 1989. Two hundred and thirty cases were identified from hospital discharge records with a diagnosis of primary malignant brain tumor (International Classification of Diseases, 9th revision, code 191). Four controls were exactly matched with each case on year of age and race using incidence density sampling. Potential career summary extremely low frequency (ELF) and microwave-radiofrequency (MWRF) radiation exposures were based upon the duration in each occupation and an intensity score assigned by an expert panel. Ionizing radiation (IR) exposures were obtained from personal dosimetry records.^ Relative to the unexposed, the overall age-race adjusted odds ratio (OR) for ELF exposure was 1.39, 95 percent confidence interval (CI) 1.03-1.88. A dose-response was not evident. The same was true for MWRF, although the OR = 1.59, with 95 percent CI 1.18-2.16. Excess risk was not found for IR exposure (OR = 0.66, 45 percent CI 0.26-1.72).^ Increasing socioeconomic status (SES), as identified by military pay grade, was associated with elevated brain tumor risk (officer vs. enlisted personnel age-race adjusted OR = 2.11, 95 percent CI 1.98-3.01, and senior officers vs. all others age-race adjusted OR = 3.30, 95 percent CI 2.0-5.46). SES proved to be an important confounder of the brain tumor risk associated with ELF and MWRF exposure. For ELF, the age-race-SES adjusted OR = 1.28, 95 percent CI 0.94-1.74, and for MWRF, the age-race-SES adjusted OR = 1.39, 95 percent CI 1.01-1.90.^ These results indicate that employment in Air Force occupations with potential electromagnetic field exposures is weakly, though not significantly, associated with increased risk for brain tumors. SES appeared to be the most consistent brain tumor risk factor in the USAF cohort. Other investigators have suggested that an association between brain tumor risk and SES may arise from differential access to medical care. However, in the USAF cohort health care is universally available. This study suggests that some factor other than access to medical care must underlie the association between SES and brain tumor risk. ^

Genetic susceptibility, cigarette smoking, and wood dust exposure in lung cancer: Case control analyses

This case control study was conducted to assess the association between lung cancer risk, mutagen sensitivity (a marker of cancer susceptibility), and a putative lung carcinogen, wood dust exposure. There were 165 cases (98 African-Americans, 67 Mexican-Americans) with newly diagnosed, previously untreated lung cancer, and 239 controls, frequency-matched on age, sex, and ethnicity.^ Mutagen sensitivity ($\ge$1 break/cell) was associated with a statistically significant elevated risk for lung cancer (odds ratio (OR) = 4.1, 95% confidence limits (CL) = 2.3,7.2). Wood dust exposure was also a significant predictor of risk (OR = 2.8, 95% CL = 1.2,6.6) after controlling for smoking and mutagen sensitivity. When stratified by ethnicity, wood dust exposure was a significant risk factor for African-Americans (OR = 4.0, 95% CL = 1.4,11.5), but not for Mexican-Americans (OR = 1.5, 95% CL = 0.3,7.1). Stratified analysis suggested a greater than multiplicative interaction between wood dust exposure and both mutagen sensitivity and smoking.^ The cases had significantly more breaks on chromosomes 4 and 5 than the controls did with ORs of 4.9 (95% CL = 2.0, 11.7) and 3.9 (95% CL = 1.6, 9.3), respectively. Breaks at 4p14, 4q27, 4q31, 5q21-22, 5q31, and 5q33 were significantly more common in lung cancer patients than in controls. Lung cancer risk had a dose-response relationship with breaks on chromosomes 4 and 5. Cigarette smoking had a strong interaction with breaks on chromosomes 2, 4, and 5.^ In a molecular cytogenetic study, using chromosome painting and G-banding, we showed that: (1) the proportion of chromosome 5 abnormalities surviving as chromosome-type aberrations remained significantly higher in cells of lung cancer cases (14%) than in controls (5%) (P $<$ 0.001). However, no significant differences were detected in chromosome 4 abnormalities between cases and controls; (2) the proportion of chromosome 5q13-22 abnormalities was 5.3% in the cases and 0.7% in the controls (P $<$ 0.001). 5q13-22 regions represented 40% of all abnormalities on chromosome 5 in the cases and only 14% in the controls.^ This study suggests that mutagen sensitivity, wood dust exposure, and cigarette smoking were independent risk factors for lung cancer, and the susceptibility of particular chromosome loci to mutagenic damage may be a genetic marker for specific types of lung cancer. ^