Cancer in veterinarians

Frequency of workplace incidents and injuries in veterinarians, veterinary nurses and veterinary students and measures to control these

BACKGROUND

Veterinarians, veterinary nurses and veterinary students work and train in a variety of environments and are exposed to a wide range of hazards.

OBJECTIVES

(1) To compare the rate of health and safety incidents and injuries between veterinarians, veterinary nurses and veterinary students. (2) To investigate the health and safety hazard controls present in Australian veterinary workplaces.

STUDY DESIGN

A cross-sectional study, using an online questionnaire.

METHODS

Anonymous links to the questionnaire were disseminated to Australian veterinarians, veterinary nurses and veterinary students.

RESULTS

A total of 494 veterinarians, 484 veterinary nurses and 212 veterinary students completed the survey. Incidents and injuries were common, particularly sharps-related injuries and animal bites. Australian veterinary nurses and veterinarians experienced the studied incidents at similar rates to each other. Veterinary students experienced some incidents and injuries at rates higher than both veterinarians and veterinary nurses, including heatstroke, hypothermia, sunburn, electric shock, loss of consciousness, being rammed or pushed over by an animal and farm equipment injuries. Of the workplace hazard controls reported, first aid boxes were most commonly present, and safety meetings occurred least commonly. Veterinary nurses received Q fever and rabies vaccines much less frequently than veterinarians and veterinary students.

CONCLUSION

This study demonstrated that improvements need to be made to the occupational health and safety standards in the Australian veterinary sector. Veterinarians and veterinary nurses had suboptimal rates of access to many of the required and critical workplace health and safety controls. Improvements to the standard of health and safety training of veterinary students are indicated, given their higher rates of certain incidents and injury.

Pathogenic mechanisms and etiologic aspects of Mycobacterium avium subspecies paratuberculosis as an infectious cause of cutaneous melanoma

Infectious etiologies have previously been proposed as causes of both melanoma and non-melanoma skin cancer. This exploratory overview explains and presents the evidence for the hypothesis that a microorganism excreted in infected ruminant animal feces, Mycobacterium avium subspecies paratuberculosis (MAP), is the cause of some cases of cutaneous melanoma (CM). Occupational, residential, and recreational contact with MAP-contaminated feces, soil, sand, and natural bodies of water may confer a higher rate of CM. Included in our hypothesis are possible reasons for the differing rates and locations of CM in persons with white versus nonwhite skin, why CM develops underneath nails and in vulvar skin, why canine melanoma is an excellent model for human melanoma, and why the Bacille Calmette-Guérin (BCG) vaccine has demonstrated efficacy in the prevention and treatment of CM. The pathogenic mechanisms and etiologic aspects of MAP, as a transmittable agent underlying CM risk, are carefully deliberated in this paper. Imbalances in gut and skin bacteria, genetic risk factors, and vaccine prevention/therapy are also discussed, while acknowledging that the evidence for a causal association between MAP exposure and CM remains circumstantial.

Results of routine thoracic radiographic examinations rarely impact the plan to proceed with anesthetic procedures in dogs with presumed acute intervertebral disc herniation

Introduction

Acute thoracolumbar intervertebral disc herniation (IVDH) constitutes an emergency because associated neurological clinical signs can be progressive, with prognosis dependent on preoperative presence of deep pain perception. Pre-anesthetic thoracic radiographs are routinely performed to evaluate for potential pathology that could result in increased risk or change in overall prognosis. However, due to the emergent nature of this disease, the weight of thoracic radiographic findings on treatment plans for these dogs in unknown. The objective of this study was to investigate the clinical benefit of thoracic radiographs prior to advanced spinal imaging and surgery for acute non-ambulatory dogs with suspected T3-L3 myelopathy.

Methods

Consecutive dogs presented with presumed acute IVDH between July 2020-July 2022 were identified, and medical records were reviewed retrospectively. Age, body weight, and alteration of treatment plan were compared between the dogs with positive thoracic pathology identified on thoracic radiographs and those with negative thoracic pathology.

Results

Only 2/105 dogs had their diagnostic and treatment plans changed due to thoracic radiographic findings. Dogs with radiographic pathology diagnosed (2/16) were more likely to have their treatment plans changed than dogs with no radiographic pathology (0/89) (p = 0.014). The odds of radiographic thoracic pathology were 4.6 times higher in dogs aged 12 years or older [OR 4.6 (95%CI 1.2-17, p = 0.026].

Discussion

Performing routine thoracic radiography prior to advanced (anesthetized) diagnostic spinal imaging in presumed IVDH cases rarely resulted in a change to the treatment plan, thought eh practice may be clinically relevant in dogs 12 years of age or older.

No Excess Cancer Risk among Veterinarians in Denmark, Finland, Iceland, Norway, and Sweden after the 1980s

The cancer profile of veterinarians has received little research attention, despite the profession potentially being exposed to a wide range of known and suspected carcinogens. In this large-scale cohort study, we assessed cancer incidence in veterinarians in Denmark, Finland, Iceland, Norway, and Sweden, across more than 40 years (1961-2005). The cohort comprised 4708 veterinarians and 119,503 person-years at follow-up. The overall cancer incidence in veterinarians was close to the incidence in the total population in all countries and in all age groups. In male veterinarians, the standardized incidence ratios (SIR) in 1961-1990 were elevated for colon cancer (1.86, 95% confidence interval (CI) 1.39-2.44), prostate cancer (1.35, 95% CI 1.07-1.67), and especially skin melanoma (3.62, 95% CI 2.78-2.84), while there was no longer any statistically significant excess in the more recent follow-up period. Decreased SIRs were observed for lip cancer (0.11, 95% CI 0.00-0.62), laryngeal cancer (0.38, 95% CI 0.12-0.89), lung cancer (0.59, 95% CI 0.47-0.74), and stomach cancer (0.58, 95% CI 0.38-0.86), without a marked change in SIR over time. Non-significant excesses among male veterinarians were also observed in Hodgkin lymphoma (1961-1990 only), and leukaemia. This multi-country study indicates that there was an elevated incidence of several cancer types among male veterinarians before the 1990s but not after that. Some of the findings might rather be attributed to lifestyle factors and not directly to work conditions, but the excess risk of cancers of kidney and bladder, for example, might be related to work exposures.

A case-control study of occupational risk factors for pancreatic cancer in poultry plant workers: a random forest approach

BACKGROUND

Poultry plant workers are exposed to chemical carcinogens and oncogenic viruses in their work environment. Our objective was to identify jobs and workplaces related to poultries that could increase the pancreatic cancer risk.

METHODS

We conducted a case-control study within a defined cohort of poultry workers. We used a random forest algorithm to identify features that could increase pancreatic cancer in the poultry plant workers.

RESULTS

The mean age of participants was 59.49 years. The majority of the study participants were females (51.30%) and Whites (71.0%). The following workplaces and job tasks had an association with increased pancreatic cancer mortality: working in chicken and turkey plants, working in plants where food products were processed and canned, working in a place where poultry and animals where present, working as a hunter for game animals, working as a veterinarian in places had animals and different poultry birds, working in pet houses and working in places where birds were handled and killed. The accuracy and the area under the curve of the model were 72.3 and 71.50%.

CONCLUSION

Chicken and turkey plant workers could be at risk for pancreatic cancer mortality. We need to confirm the results in future studies.

Most students have experience making radiographs prior to veterinary school but have limited radiation safety training

The use of radiation for the diagnosis of various medical conditions is ubiquitous in veterinary medicine, and manual restraint of a patient during X-ray exposure has become commonplace. Many prospective veterinary students have been involved with radiographs in general practice prior to veterinary school. Their experiences and level of safety training are largely unknown.   This prospective survey study involved two web-based questionnaires that were used to evaluate the experiences, knowledge, and attitudes toward radiation and how these changed following a radiation safety lecture as part of their first-year curriculum. The questionnaires were distributed to 122 first-year veterinary students before and after this lecture. All participating students (100%) had worked in a veterinary hospital prior to admission to veterinary school and 79% were involved in making radiographs; however, only 28% reported receiving radiation safety training. The content of the safety training reported was variable. After the radiation safety lecture, students were more likely to report that the radiation safety training they had received was useful, but fewer students reported feelings of safety when using radiation. Despite most students being involved with radiation in practice, few had received radiation safety training, as hypothesized. Contrary to our second hypothesis, a single lecture did significantly improve knowledge and attitudes in several, but not all, instances. Importantly, once students gained knowledge regarding radiation, they placed more importance on its safe use. These results suggest that in-clinic training of students in radiation safety is insufficient and that lecture-based training is useful for certain concepts.

Imaging diagnosis of canine hip dysplasia with and without human exposure to ionizing radiation

Hip dysplasia (HD) is one of the most common hereditary orthopaedic diseases in dogs, with serious implications for the quality of life of the affected animals. Radiographic screening is essential for the selection of breeding stock in some at-risk breeds, and radiography is also used in the diagnosis of clinical HD cases. A definitive diagnosis of HD is based on radiographic examination, and the most commonly used view is the ventrodorsal hip extended projection, sometimes in combination with various hip stress-based techniques. Radiographic images require high quality positioning and dogs are usually anesthetized and often manually restrained to facilitate optimal positioning. The 'as low as reasonably achievable' (ALARA) principle used in human radioprotection is not always fulfilled in veterinary practice, except in the UK, where human exposure to ionizing radiation in veterinary medicine is strictly regulated. While each dose of ionizing radiation is small, doses accumulate over a lifetime, which can eventually result in substantial radiation exposure. Therefore, manual restraint should be avoided and mechanical immobilization, sedation or general anaesthesia should be used. This review examines the biological effects of human exposure to ionizing radiation and common sources of veterinary exposure. The diagnostic quality of imaging methods for the diagnosis of canine HD is compared between manually restrained and hands-free dog positioning. Hands-free radiographic techniques are available to assess hip laxity, degenerative joint changes and hip osseous structure while preserving image quality, and can be used to select animals for breeding or for the diagnosis of HD.

Systematic review and meta-analysis of veterinary-related occupational exposures to hazards

Understanding hazards within the veterinary profession is critical for developing strategies to ensure the health and safety of personnel in the work environment. This study was conducted to systematically review and synthesize data on reported risks within veterinary workplaces. A systematic review of published data on occupational hazards and associated risk factors were searched within three database platforms namely PubMed, Ebscohost, and Google scholar. To determine the proportion estimates of hazards and pooled odds ratio, two random-effects meta-analysis were performed. For the biological, chemical and physical hazards, the pooled proportion estimates were 17% (95% CI: 15.0-19.0, p < 0.001), 7.0% (95% CI: 6.0-9.0%, p < 0.001) and 65.0% (95% CI: 39.0-91.0%, p < 0.001) respectively. A pooled odds ratio indicated the risk of exposures to physical (OR=1.012, 95% CI: 1.008-1.017, p < 0.001) and biological hazards (OR=2.07, 95% CI: 1.70-2.52, p <0.001) increased when working or in contact with animals. The review has provided a better understanding of occupational health and safety status of veterinarians and gaps within the developing countries. This evidence calls for policy formulation and implementation to reduce the risks of exposures to all forms of occupational-related hazards in veterinary workplaces.

Hands-Free Conventional Radiographic Ventrodorsal Hip Extended View

Hip dysplasia (HD) is an important hereditary orthopedic disease in the dog associated with osteoarthritis and inadequate welfare for affected animals. The radiographic ventrodorsal hip extended (VDHE) view is used worldwide to select the better animals for breeding. This view normally is performed with manual restraining of the dog to obtain radiographs with acceptable technical quality. The veterinarian exposition to ionizing radiation is inevitable. In this study, the technical quality of VDHE radiographs and hip measurements was compared in 65 dogs radiographed twice, one with the common veterinarian manual restraining and the other obtained using a hind limb holder device, without the veterinarian within the X-ray room. The variables studied were pelvic tilting, patella displacement index, Norberg angle (NA), and subluxation hip category. The results showed a random distribution of right and left pelvic tilting, patella lateral or medial displacement, and hip subluxation categories in both samples (P > 0.05). The holder device positioning showed a better pelvic symmetry (P < 0.05) and a similar patellar displacement (P > 0.05). The mean ± standard deviation of NA was 101.1° ± 6.2° and 100.9° ± 6.1° in the manual and holder device hind limb restraining, respectively (P > 0.05), and the lower limit of 95% confidence interval of intraclass correlation coefficient was >0.75. These results showed statistical reproducibility of NA measurements by the hind limb holder device, and the examiner was protected from exposure to ionizing radiation within the X-ray room.

Determinants of Work-Related Risks among Veterinary Clinical Students in South West Nigeria

Veterinary practices or activities expose professionals, including students, to hazards associated with animal contact. To describe workplace health and safety status and risk factors associated with hazards among veterinary clinical students in South West Nigeria, a cross-sectional survey was conducted using a semistructured questionnaire. Data on demographics, health and safety (HS) status, work-related hazards, healthcare facilities, and immunisation history were obtained. Of 167 students recruited, 100 (60.2%) were males, and >77.1% fell within the age group of 21-25 years. Many participants (77.0%) reported the lack of active HS committee. Exposures to various physical hazards (PHs) such as needlestick injuries (NSIs, 41.5%), animal scratches (42.0%), animal kicks (33.0%), falls/slips (25.0%), and, less frequently, animal bites (13.8%) were reported. Allergies (35.9%) and acute gastrointestinal infection (25.6%) mainly after contact with dogs presented with parvoviral enteritis were reported. For chemical hazards, 27.8% and 29.0% of participants indicated having had eye burn and choke on exposure to formalin. No adequate immunisation against either tetanus, rabies, or both was provided (<18%). An association between accommodation type and students' level of health and safety training was observed (OR = 0.46, 95% CI: 0.241-0.897, p=0.02), and frequencies of student contact with various animal types were strongly associated with exposures to different physical and biological risks (p < 0.05). This study revealed poor health and safety training, practices, and increased exposure of students to a wide range of hazards. Therefore, the development of mitigation programmes in veterinary schools becomes critical to safeguard students' wellbeing.

RADIATION DOSE DISTRIBUTION OF A PLAIN RADIOGRAPHY ROOM AND COMPUTED TOMOGRAPHY ROOM IN A VETERINARY HOSPITAL

Thermoluminescent dosemeters (TLDs) were attached to the walls of a plain radiography room and a computed tomography (CT) room, control rooms and corridors to measure the radiation dose. The types of animals scanned and scan parameters were analysed. Dogs and cats accounted for the largest proportion of animals, a combined total of 96.0%. Distributions of tube voltage and tube current-time product are presented. In the CT room, the dose at the angle of the gantry opening was higher than that on either side of the gantry. The study developed equations that may be useful to assess the dose for staff standing in radiography rooms. The personal annual doses for the controlled and uncontrolled areas were lower than the recommended dose limit. The annual doses for personnel and nonworkers were also within the acceptable level for radiation safety.

ACVIM small animal consensus statement on safe use of cytotoxic chemotherapeutics in veterinary practice

The purpose of this report is to offer a consensus opinion of ACVIM oncology diplomates and technicians on the safe use of cytotoxic chemotherapeutics in veterinary practice. The focus is on minimizing harm to the personnel exposed to the drugs: veterinary practitioners, veterinary technicians, veterinary staff, and pet owners. The safety of the patient receiving these drugs is also of paramount importance, but is not addressed in this statement. Much of the information presented is based on national recommendations by Occupational Safety and Health Administration, National Institute for Occupational Safety and Health, United States Pharmacopeia, and other published regulations. These directives reflect an abundance of caution to minimize exposure to medical personnel, but large-scale studies about the consequences of long-term occupational exposure are not available in veterinary medicine. Challenges in the delivery of optimal treatment safely and economically to veterinary patients in general practice without access to a veterinary oncologist or other specialist, because of costs or proximity, remain.

Contact with animals and risk of oesophageal squamous cell carcinoma: outcome of a case-control study from Kashmir, a high-risk region

BACKGROUND

Several studies have reported association between animal contact and some cancer types, including lymphohaematopoietic, colon, pancreatic and neurological malignancies. We aimed to investigate the association between animal contact and risk of oesophageal squamous cell carcinoma (ESCC) in a case-control study in Kashmir, India, area with a relatively high incidence of ESCC.

METHODS

We recruited 703 histologically confirmed ESCC cases and 1664 controls individually matched to the cases for age, sex and district of residence. Information, including on animal contact, was obtained in face-to-face interviews using a structured questionnaire. Conditional logistic regression models were used to calculate ORs and 95% CIs.

RESULTS

As compared with no contact with animals, daily close contact was associated with an increased risk of ESCC (OR 5.99; 95% CI 3.86 to 9.31) in models adjusted for several potential confounding factors, including multiple indicators of socioeconomic status. This association persisted in subgroups following stratification by a composite wealth score and occupation. Irregular contact with animals was not associated with ESCC risk. The association between duration of animal contact and ESCC risk was mixed; however, contact for more than 50 years was associated with an increased risk (OR 3.10; 95% CI 1.53 to 6.26). Frequency (p for trend, 0.001) and duration (p for trend, <0.001) of animal contact showed dose-response association with ESCC risk.

CONCLUSIONS

Our results suggest an association between long-term and daily close contact with animals and ESCC. This association needs to be investigated in further studies.

Occupational exposures to antineoplastic drugs and ionizing radiation in Canadian veterinary settings: findings from a national surveillance project

OBJECTIVES

Although veterinary workers may encounter various occupational health hazards, a national characterization of exposures is lacking in Canada. This study used secondary data sources to identify veterinary exposure prevalence for ionizing radiation and antineoplastic agents, as part of a national surveillance project.

METHODS

For ionizing radiation, data from the Radiation Protection Bureau of Health Canada were used to identify veterinarians and veterinary technicians monitored in 2006. This was combined with Census statistics to estimate a prevalence range and dose levels. For antineoplastic agents, exposure prevalence was estimated using statistics on employment by practice type and antineoplastic agent usage rates, obtained from veterinary licensing bodies and peer-reviewed literature.

RESULTS

In 2006, 7,013 (37% of all) Canadian veterinary workers were monitored for ionizing radiation exposure. An estimated 3.3% to 8.2% of all veterinarians and 2.4% to 7.2% of veterinary technicians were exposed to an annual ionizing radiation dose above 0.1 mSv, representing a total of between 536 and 1,450 workers. All monitored doses were below regulatory limits. For antineoplastic agents, exposure was predicted in up to 5,300 (23%) of all veterinary workers, with an estimated prevalence range of 22% to 24% of veterinarians and 20% to 21% of veterinary technicians.

CONCLUSION

This is the first national-level assessment of exposure to ionizing radiation and antineoplastic agents in Canadian veterinary settings. These hazards may pose considerable health risks. Exposures appeared to be low, however our estimates should be validated with comprehensive exposure monitoring and examination of determinants across practice areas, occupations, and tasks.

Research at the interface between human and veterinary health

Epidemiology is currently undergoing changes in its underlying philosophy and approach, as a result of the rapid global changes which are transforming the world in which epidemiologists live and work. This necessitates a multidisciplinary "population approach" involving "multilevel thinking" about the determinants of disease. These issues are of relevance to the interface between human and animal epidemiology, which has received considerable attention in recent years, particularly as a result of the arrival of H1N1 influenza, and the increasingly obvious need for coordinated systems of surveillance for human and animal infectious diseases. However, the need for coordination between human and veterinary epidemiology is broader than that, and there is no need to restrict the "one world one health" concept to communicable disease. In the current paper we will therefore consider the interface between human and animal health for the study of non-communicable disease, particularly those involving occupational and environmental risk factors. These issues are illustrated with two examples: one involving environmental health (asthma); and one involving occupational health (cancer). We will also discuss the potential to use animal health data as indicators for human environmental health risks.

Occupational health hazards in veterinary medicine: physical, psychological, and chemical hazards

This paper reports physical, psychological, and chemical hazards relevant to western Canadian veterinarians as obtained by a self-administered mailed questionnaire. Nine-three percent (750/806) of veterinarians reported some form of injury during the previous 5 years; 17% of respondents (131/791) indicated injuries that resulted in 1 or more days off work. Median stress levels were similar across work environments; overall, 7% (57/813) indicated either no stress or severe stress, while 53% (428/813) indicated moderate stress. Twenty percent (3/15) of food animal practitioners and 37% (114/308) of companion animal practitioners who took X-rays reported accidental exposure. Accidental exposure to gas anesthetic was reported by 69% (394/570) of those in private practice. Exposure to chemicals occurred in all work environments. Veterinarians in western Canada are at risk of minor to severe injury due to both animal and non-animal related causes.

Understanding attraction stimuli of the cat flea, Ctenocephalides felis, in non-chemical control methods

Comparisons were conducted of flea catches of four commercially available flea traps in the laboratory and under field conditions, in both rural and urban locations. The results clearly showed the My Flea Trap™, which utilizes an intermittent light to attract fleas, to be far superior in trapping ability to the three continuous light traps; it caught up to 23 times as many fleas as the other traps. Altering the lighting mechanism to provide continuous rather than intermittent light significantly decreased the number of fleas captured. In addition, the use of a green filter significantly increased trapping efficiency, whereas the addition of a heat source had no apparent effect.

Feline head and neck squamous cell carcinoma: a natural model for the human disease and development of a mouse model

Head and neck squamous cell carcinoma (H/N SCC) is a devastating disease in humans and cats, and shares similar features between the two species. The large population of pet cats in the United States, along with the high incidence of oral SCC in the cat, makes the cat an attractive candidate as a natural model for the human disease. There are similarities in pathology, progression, outcome, resistance to treatment, possible aetiologies and p53 expression, and we discuss the benefits of the cat as a natural model. We describe the development of a nude mouse xenograft model of feline oral SCC using the SCCF1 cell line transfected with a luciferase expression construct. In vivo tumour growth and metastasis were measured using serial bioluminescent imaging, and tumours grew best in the subcutis. The cat and nude mouse models will be useful to investigate the pathogenesis and the molecular basis of H/N SCC, and for preclinical drug screening.

Prevalence of occupational exposures and protective practices in Australian female veterinarians

OBJECTIVE

To identify the prevalence of exposure to potentially harmful occupational hazards in Australian female veterinarians and to report factors associated with prevalence of occupational hazards in this profession.

DESIGN

National cross-sectional survey of a cohort population.

PROCEDURE

A self-administered questionnaire was mailed to 5748 veterinarians (males and females) graduating from Australian veterinary schools from 1960 to 2000. This paper reports the prevalence of occupational exposures in 1197 female veterinarians in their current job including radiation, anaesthetic gases, pesticides and long working hours. Comparisons were undertaken between respondents by practice type and decades of graduation. Multivariate logistic regression was undertaken to predict the risk for exposure to occupational hazards in female veterinarians by age, type of practice, graduation year and number of hours worked.

RESULTS

The response rate for females was 59%. We found that age under 30 years, small and mixed animal practice, graduation year after 1990, and working more than 45 hours per week were all associated with greater exposure to putative risk factors. Mixed animal practitioners worked more than 45 hours per week (53%) and reported the highest exposure to anaesthetic gases (94%) and pesticides (54%). Twenty two percent of those who were exposed to anaesthetic gases did not have waste anaesthetic gas scavenging systems. Small animal practitioners reported they took more X-rays (90%). While taking X-rays, 56% of respondents reported physically restraining animals, and only one in five of respondents used film holders and lead screens.

CONCLUSIONS

The high prevalence of potentially harmful exposures among female veterinarians and lack of use of protective equipment at work needs to be considered in developing and planning the safety of veterinary work.

Occupational health risks in veterinary nursing: an exploratory study

OBJECTIVES

The aims of this exploratory study were to survey the prevalence of certain exposures and health problems among a group of veterinary nurses attending the International Veterinary Nurses' Conference in Brisbane, Australia, 2003 and to identify the main concerns among those veterinary nurses with regard to occupational health hazards they may face.

METHODS AND MATERIALS

An anonymous self-administered questionnaire was distributed among all attendees of the International Veterinary Nurses' Conference 2003, Brisbane, Australia (N=147 respondents among 215 surveyed).

RESULTS

The prevalence of exposure to X-radiation (97%), anaesthetics (96%), disinfectants (96%) and vaccines (85%) was high. More than 70% of the nurses were exposed to formaldehyde (76%) and pesticides/insecticides (71%). For all exposures except vaccines, about 50% of the nurses exposed were worried about negative health consequences. Acute injuries were common with 98% of the nurses experiencing dog/cat bites/scratches, 71% experiencing needle stick injuries and 43% experiencing lacerations. More than half of the nurses (52%) suffered from chronic back/neck pain and 39% reported having allergy or hay fever. Sixteen cases (11%) of Cat Scratch Fever were reported. Job related affective well-being was similar to a large sample of workers in comparable level jobs.

CONCLUSION

Among attendees of a veterinary nurses conference, the proportion of this group of nurses exposed to hazards in their work environment was high and acute and chronic injuries were common. Considering that nurses account for more than 40% of total employment in the veterinary service industry, the results of this study show that the occupational health hazards of this professional group require further study.