Factors associated with chronic and acute back pain in Wales, a cross-sectional study.

BACKGROUND: Back pain is one of the most common causes for disability in the working population. Some risk factors for back pain are well known, however little is known about factors uniquely associated with acute or chronic back pain. This study aimed to elucidate patterns uniquely associated with acute or chronic back pain. METHODS: This study performed secondary analysis of data from the Welsh Health Survey 2012, a nationwide cross-sectional survey. A multivariable analysis was carried out for risk factors found to be significantly associated with acute and chronic back pain. RESULTS: We found that increased BMI (aOR 1.20, 95% Cis 1.08, 1.33; BMI > 30), mental health score below average (aOR 1.59, 95% CIs 1.47, 1.72), having a degree (aOR 1.28, 95% CIs 1.12, 1.47) and being older than 24 years (P < 0.001) were associated with increased prevalence of acute back pain. Higher prevalence of chronic back pain was seen in individuals characterised by increased deprivation (WIMD) (aOR 1.61, 95% CIs 1.32, 1.96); increased age (aOR 7.34, 95% CIs 5.25, 10.26; for 65+); being female (aOR = 1.43, 95% CIs 1.27, 1.61); lower educational attainment (aOR 0.44, 95% CIs 0.36, 0.55) higher BMI (aOR = 1.60 95% CIs 1.38, 1.85; BMI > 30); poorer mental health score (aOR = 3.11 95% CIs 2.76, 3.51), and a sedentary lifestyle (aOR = 0.58, 95% CIs 0.49, 0.69; 3-5 days of light exercise). CONCLUSION: Increased deprivation, female gender, and little exercise were uniquely associated with chronic back pain. These characteristics may help clinicians to intervene to prevent acute backpain resulting in chronic cases.

[Asbestos and its effects on health of Icelanders - review].

Asbestos are crystallized silicate minerals that form fibers with different structures and characteristics. Asbestos fibers are very durable and can tolerate very high temperatures. Therefore it was common to use asbestos as a fire retardants, heat insulation and where high temperature is used. Asbestos has been banned in Iceland from 1983 but can still be found in large amounts in buildings, ships and hot water pipes. Large amounts of asbestos were imported in the years before the ban but diminished soon to almost nothing today. Needle or filamentous shaped dust is released when working with asbestos. It is this dust that is dangerous for health. The latent time from exposure to disease can be up to forty years. Asbestos reaches the lungs via inhalation and can cause asbestosis that is a form of lung fibrosis with slow progression. Asbestos can also cause benign pleural effusions, pleural plaques and diffuse pleural thickening. Asbestos is a carcinogen. Lung cancer is most common but asbestos is also a risk factor for cancers of other organs. Mesothelioma is most common in the pleura but can be seen in other membranes. The incidence of these tumors is high in Iceland and is still increasing among males. Of all the European countries mortality is highest in Iceland. It is important for physicians to include asbestos exposure in the differential diagnosis of lung diseases and when lung cancer is diagnosed.

[Economic crises and incidence of suicide in Iceland 1911-2017]. / Efnahagskreppur og tíðni sjálfsvíga á Íslandi 1911-2017

INTRODUCTION: Suicides are number 16 as a cause of death worldwide. Causes are not always known, often associated with depression or trauma. Suicide incidence has decreased world- wide in the past three decades. The economic crisis of 2008 led to an increase in many countries. Many confounding factors make comparisons between countries difficult. This study assesses the possible impact of economic crises in Iceland on suicide incidence. MATERIAL AND METHODS: The work is based on suicide data from 1911 to 2017 and six economic crises from 1918 to 2008. The incidence is calculated five and ten years before and after the index year of each crisis. Possible crisis impact was assessed by applying a quasi-Poisson model to the data. Variance can be greater than model shows, so overdispersion was assessed. The evolution over time is assessed by inspection of cumulative sum of squared -residuals (CUSUMSQ). RESULTS: Suicide incidence increased from 1930, beginning to decline around 1990. Given a small population size there are wide upwards incidence fluctuations, within and outside the crisis -periods. The crises of 1931 and 1948 showed an increase, wheras in the others there is no change or a decrease. The sizes of deviations from expected value are, for the whole period, in compliance with the quasi-poisson model for counts. CONCLUSION: There is no statistical correlation between the six economic crises and suicide incidence in the Icelandic data. The study is based on population incidence and does not preclude a negative impact of economic crises on individuals.

Research priorities for public mental health in Europe: recommendations of the ROAMER project.

BACKGROUND: The ROAdmap for MEntal health Research in Europe project aimed to create an integrated European roadmap for mental health research. Leading mental health research experts across Europe have formulated consensus-based recommendations for future research within the public mental health field. METHODS: Experts were invited to compile and discuss research priorities in a series of topic-based scientific workshops. In addition, a Delphi process was carried out to reach consensus on the list of research priorities and their rank order. Three web-based surveys were conducted. Nearly 60 experts were involved in the priority setting process. RESULTS: Twenty priorities for public mental health research were identified through the consensus process. The research priorities were divided into summary principles-encompassing overall recommendations for future public mental health research in Europe-and thematic research priorities, including area-specific top priorities on research topics and methods. The priorities represent three overarching goals mirroring societal challenges, that is, to identify causes, risk and protective factors for mental health across the lifespan; to advance the implementation of effective public mental health interventions and to reduce disparities in mental health. CONCLUSIONS: The importance of strengthening research on the implementation and dissemination of promotion, prevention and service delivery interventions in the mental health field needs to be emphasized. The complexity of mental health and its broader conceptualisation requires complementary research approaches and interdisciplinary collaboration to better serve the needs of the European population.

The impact of economic factors on migration considerations among Icelandic specialist doctors: a cross-sectional study.

BACKGROUND: Globalization has facilitated the employability of doctors almost anywhere in the world. In recent years, the migration of doctors seems to have increased. However, we lack studies on doctors' migration from developed countries. Because the economic recession experienced by many countries might have affected the migration of doctors, research on this topic is important for the retention of doctors. Iceland was hit hard by the economic recession in 2008. Therefore, we want to explore how many specialist doctors in Iceland have considered migrating and whether economic factors at work and in private life, such as extensive cost-containment initiatives at work and worries about personal finances, are related to doctors' migration considerations. METHODS: In 2010, all doctors in Iceland registered with the Icelandic Medical Association were sent an electronic cross-sectional survey by email. The 467 specialists who participated in this study represent 55% of all specialist doctors working in Iceland. Information on doctors' contemplation of migration was available from responses to the question: "Have you considered moving and working abroad?" The predictor variables in our logistic regression model are perceived cost-containment initiatives at work, stress related to personal finances, experience of working abroad during vacations, job dissatisfaction, job position, age, and gender. RESULTS: Sixty-three per cent of Iceland's specialist doctors had considered relocation abroad, 4% were moving in the next year or two, and 33% had not considered relocating. Logistic regression analysis shows that, controlling for age, gender, job position, job satisfaction, and experience of working abroad during vacations, doctors' migration considerations were significantly affected by their experiences of cost-containment initiatives at work (odds ratio (OR) = 2.0, p < 0.01) and being stressed about personal finances (OR = 1.6, p < 0.001). Age, job satisfaction, and working abroad during vacations also had an effect, whereas job position did not. CONCLUSIONS: Economic factors affect whether specialist doctors in Iceland consider migration. More studies on the effect of economic recession on migration by doctors are needed.

Financial crisis and collapsed banks: psychological distress and work related factors among surviving employees--a nation-wide study.

AIM: The study considered psychological distress among surviving bank employees differently entangled in downsizing and restructuring following the financial crisis of 2008. METHODS: A cross-sectional, nationwide study was conducted among surviving employees (N = 1880, response rate 68%). Multivariate analysis was conducted to assess factors associated with psychological distress. RESULTS: In the banks, where all employees experienced rapid and unpredictable organizational changes, psychological distress was higher among employees most entangled in the downsizing and restructuring process. Being subjected to downsizing within own department, salary cut, and transfer to another department, was directly related to increased psychological distress, controlling for background factors. The associations between downsizing, restructuring, and distress were reduced somewhat by adding job demands, job control, and empowering leadership to the model, however, adding social support had little effect on these associations. CONCLUSION: Employees most entangled in organizational changes are the most vulnerable and should be prioritized in workplace interventions during organizational changes.

Long-term outcome of medically confirmed and self-reported early traumatic brain injury in two nationwide samples.

PRIMARY OBJECTIVES: To assess long-term effects of early traumatic brain injury (TBI) on mental health, cognition, behaviour and adjustment and to identify prognostic factors. METHODS AND PROCEDURES: A 1-year nationwide cohort of all 0-19 year old Icelandic children and adolescents diagnosed with TBI in 1992-1993 (n = 550) received a questionnaire with clinical outcome scales and questions on TBI and socio-economic status (SES) by mail ∼16 years post-injury. A control group (n = 1232), newly selected from the National Registry, received the same questionnaire. Non-respondents answered a shorter version by telephone. Overall participation was 67%. MAIN OUTCOMES AND RESULTS: Medically confirmed and self-reported TBI was reflected in worse outcome. Force of impact, number and severity of TBIs predicted poorer results. Parental SES and demographic factors had limited effects. Not reporting early, medically confirmed TBI did not exclude cognitive sequelae. In self-reported disability, absence of evaluation for compensation was not linked to outcome. CONCLUSIONS: Clinical outcome was consistent with late complaints attributed to early TBI. TBI-related variables had greater prognostic value than other factors. Self-reporting of TBI sustained very early in life needs supplementary information from parents and medical records. More consistency in compensation evaluations following paediatric TBI is indicated.

The scope of early traumatic brain injury as a long-term health concern in two nationwide samples: prevalence and prognostic factors.

PRIMARY OBJECTIVES: To examine the scope of paediatric traumatic brain injury (TBI) as a health concern and to identify prognostic factors for TBI-related sequelae. METHODS AND PROCEDURES: The study was prospective and nationwide. A questionnaire was sent to a study group (SG) of all 0-19 years old in Iceland, diagnosed ∼16 years earlier with TBI during a 1-year period, 1992-1993 (n = 550) and to a control group (CG) (n = 1232), selected from the National Register. MAIN OUTCOMES AND RESULTS: In the CG 49.5% reported having sustained TBI and 7.0% reported long-term disability. In the group with TBI, force of impact to the head, more than one incident of TBI and the injury severity by gender interaction predicted late symptoms. TBI severity had substantially less effect than force of impact and was close to non-existent for females. CONCLUSIONS: Based on two independent nationwide samples, the scope of TBI as a health concern in adolescence and young adulthood is greater than previously documented. The findings suggest that TBI event-related factors, especially force of impact, have greater predictive value than clinical symptoms of severity at the acute stage, females being more sensitive to the effects of mild TBI than males.

Increased incidence of disability due to mental and behavioural disorders in Iceland 1990-2007.

AIMS: To explore longitudinal changes in the importance of mental and behavioural disorders and their subgroups among people receiving disability pension in Iceland in the period 1990 to 2007. METHOD: Estimation of the incidence of disability pension was based on national demographic data and information from the national disability register which includes the main diagnoses causing disability. RESULTS: The share of mental and behavioural disorders among new recipients of disability pension increased from 14 to 30% for women and 20 to 35% men. There was a marked increase in the incidence of disability due to disorders related to the use of alcohol and other psychoactive substances, mood disorders, disorders of psychological development and behavioural and emotional disorders with onset usually occurring in childhood and adolescence. The proportion of mental and behavioural disorders as the primary diagnosis among new recipients of disability pension increased. CONCLUSION: The most likely explanation for the changes we observe is alteration in social conditions leading to a lower threshold for seeking disability pension for mental disorders.

Epidemiology of psychotropic medication use: comparison of sales, prescriptions and survey data in Iceland.

Public health issues, medical and socio-demographics, related to use of psychotropic medications and to increasing sale of antidepressants and hypnotics need to be explored. The aim of this study was to investigate the use of antidepressants, tranquillizers and sedatives nationally and its connection with health and demographic factors, by comparing: 1) sales data and 2) prescription data for outpatients with 3) self-reported use of a random sample of the population aged 18-75 years. In 2001, the sales of psychopharmaca was 168.8 daily defined doses (DDD)/1000/day, thereof 46.6% were antidepressants mainly for outpatients; one-third of hypnotics and tranquillizers were used for inpatients; 134.2 DDD/1000/day were filled by outpatients. Almost 20% of the respondents in the survey had used one or more of these drugs for some time during the preceding 12 months. Treatment adherence for antidepressants was 56%, lower for women than men. The probability of psychotropic drug use for mental complaints is 52% when controlled for other covariates. Any observed gender difference in the community survey is related to differences in the covariates, e.g. women are more likely to seek a doctor than men. The age effect on self-reported use in the community survey is related to hypnotics. The use of psychotropic medicaments is primarily driven by mental health complaints, but not by gender or age, except the use of hypnotics, which increases with age. The difference between self-reported use and prescriptions filled may reflect compliance problems in psychiatric treatment.

Lifestyle, harassment at work and self-assessed health of female flight attendants, nurses and teachers.

Health-related lifestyle, harassment at work, and self-assessed health of female flight attendants in comparison to that of female nurses and female primary school teachers were surveyed. A higher proportion of flight attendants than nurses or teachers were smokers, 26% vs. 15% and 17% respectively; and consumed alcohol at least once a week, 40% vs. 21% and 16%. Repeated sexual harassment at work was more common among the flight attendants, 31% vs. 8% and 4%; whereas bullying, physical violence and threats were less prevalent among the flight attendants (12%) than among nurses (19%). Flight attendants were on average somewhat taller, but weighed on average less, 63.8 kg vs. 72.4 kg and 72.7 kg respectively. Repeated exposure to sexual harassment, bullying, violence and threats was related to less physical and psychological well-being in all the groups. Teachers scored on average significantly lower than did the flight attendants on general health and physical well-being, while nurses did not.

Malignant mesothelioma incidence by nation-wide cancer registry: a population-based study.

BACKGROUND: Malignant mesothelioma caused by asbestos exposure has a long latency period. A ban on asbestos use may not be apparent in decreased incidence in the population until after several decades. The aim was to evaluate changes in the incidence of malignant mesothelioma, and the possible impact of the asbestos ban implemented in Iceland in 1983. METHODS: This is a population study on aggregate level; the source of data was the Icelandic Cancer Registry, the National Cause-of-Death Registry, and the National Register. Volume of asbestos import was obtained from Customs Tariff. The import figures reflect fairly accurately the amount used, as there are no mines in the country. RESULTS: Asbestos import peaked in 1980 at 15.0 kg/capita/year, diminishing to 0.3 kg/capita/year ten years after the ban in 1983, and to zero in the most recent years. Seventy-nine per cent of the cases of malignant mesothelioma were men, and 72 % were of pleural origin. Mesothelioma incidence increased steadily from 1965 to 2014, when it reached 21.4 per million among men, and 5.6 among women. Mortality in 2014 was 22.2 per million among men, and 4.8 among women. CONCLUSION: Malignant mesothelioma incidence and mortality increased in the population during the period, despite the ban on asbestos use from 1983. This is in agreement with the long latency time for malignant mesothelioma. In line with the previously high per capita volume of asbestos import, many buildings, equipment, and structures contain asbestos, so there is an on-going risk of asbestos exposure during maintenance, renovations and replacements. It is thus difficult to predict when the incidence of malignant mesothelioma will decrease in the future. During the last ten-year period, the incidence in Iceland was higher than the recently reported incidence in neighbouring countries.

Mortality among female industrial workers in Iceland.

AIMS: The aim was to describe the mortality pattern among unskilled female industrial workers with the hypothesis that they were disadvantaged compared to other women and that smoking-related causes of death were in excess among them. METHODS: The study group comprised 13349 women who had contributed at any time to a pension fund for unskilled industrial workers in Reykjavik during the time period 1970-1995. The follow-up was from 1975 to 1995. The death rate of the study group was compared to that of women in the general population during the time period 1981-1995. The study group was studied with regard to selected causes of death, by age at first entrance into the pension fund, different lag-time, and by employment-time. RESULTS: Results showed an excess of external causes but a deficit of most other causes of death, among those smoking related diseases. The high mortality by external causes was consistent in all the analyses. Standardised mortality ratio (SMR) for external causes in the total group was 1.79 (95% CI 1.45-2.19), for lung cancer 1.04 (95% CI 0.80-1.34) and for ischemic heart disease 0.77 (95% CI 0.65-0.91). Mortality was highest among those who started to pay in the pension fund at younger ages. CONCLUSIONS: The notable excess of external causes in the group needs further exploration. The results did not confirm the hypothesis that smoking-related causes of death were in excess in the group. Methodological problems related to studies on women workers are discussed.

Well-being and self-assessed health among different groups of female personnel in geriatric care.

UNLABELLED: Educational qualifications are reliable predictors of women's self-assessed health. AIMS: To study possible inequalities in health among women with different educational backgrounds working in geriatric care and to find groups that might need special public health measures. METHODS: In this cross-sectional questionnaire reaching throughout Iceland, the participants were employees in 62 geriatric nursing homes and geriatric hospital wards with 10 or more employees. A total of 1886 questionnaires were distributed. The 84-item questionnaire included questions on demographic and work-related factors, health and life style. Age-adjusted odds ratios (OR) were calculated for work-related psychosocial, physical and health factors, and confidence intervals were set at 95% (95% CI). Registered nurses were taken as a reference category. RESULTS: The response rate was 80%. Registered nurses accounted for 16%, practical nurses 21%, unskilled attendants 44%, cleaning personnel 8% and others 12%. The practical nurses, unskilled attendants and cleaning personnel assessed work as more physically difficult, and more monotonous both physically and mentally, than did the registered nurses, who enjoyed more physical and mental well-being than the others. However, the registered nurses visited doctors as often as the other groups did. CONCLUSIONS: Personnel groups in geriatric care have different physical and psychosocial workloads. The results provide opportunities to guide public health measures for people employed in geriatric care and possibly in other settings, such as hospitals and health care institutions.

Work organization, well-being and health in geriatric care.

The objective of the present study was to explore the connection between the organization of work in geriatric care and factors which have been connected to job stress and burnout, i.e. exhaustion, mental workload, job satisfaction and communication. We also analyzed how these factors were related to employee visits to doctors during the previous 12 months due to various medical conditions. The study was a cross-sectional questionnaire distributed to all employees within nursing homes and geriatric hospital wards with 10 employees or more throughout Iceland. The total response rate was 80%. The majority of respondents, or 96%, were women (n = 1432), and the results are based on their answers. Our data show that there is a high correlation between mental exhaustion and the unsatisfactory organization of work. Mental exhaustion upon completing work shifts was more closely connected to the health outcomes studied than were the other work-related factors studied. This is especially true for chronic fatigue, depression and sleeping disorders. It is important that employers and managers notice the mismatches between work and workers that this study manifests. Employers and managers must also consider the organizational factors that are influential.

Lay off: the experience of women and men in Iceland's financial sector.

OBJECTIVE: To analyze gender differences in levels of psychological distress, financial strain, lay off experiences and job search activity among unemployed and re-employed individuals who were laid-off due to the collapse of the financial sector in Iceland in 2008. PARTICIPANTS: The study is based on questionnaires distributed to 759 former financial sector employees; 426 responses were received giving a 62.6% response rate. METHODS: The groups of unemployed and re-employed woman and men are compared using separate multivariate binary models to control for mediating factors. RESULTS: The analysis reveals gender differences in demographic factors and jobs held prior to lay-off. More women than men were psychologically or finically distressed and claimed being shocked by the lay-off. A higher proportion of men than women were re-employed at the time of this study. The main difference between those re-employed and unemployed was lower financial strain among those re-employed for both men and women in this sample. CONCLUSION: The study does not support the traditional view of men having more difficulties in the lay-off process than women. This calls for a rethinking regarding gender in lay-off and unemployment. A gender-based analysis is needed when considering the ramifications of losing a job and job search activity in the lay-off process.

[Mental health and wellbeing in Icelandic farmers]. / Gedheilsa og lídan íslenskra baenda.

OBJECTIVE: Some studies have suggest increased prevalence of mental health problems in farmers while others suggest, they are less common. This study aimed to determine the prevalence of mental health problems in Icelandic animal farmers. MATERIAL AND METHODS: This was a cross sectional study of all animal farmers in Iceland (response rate 54%, 1021) with an age matched comparison group (response rate 46%, 637). Psychiatric health was evaluated with General Health Questionnaire-12 and CAGE. Work conditions were studied with eight questions from the General Nordic Questionnaire for Psychological and Social Factors at Work. RESULTS: Farmers were less commonly alcohol consumers. The prevalence of mental health problems among farmers was 17 % while it was 22 % among non-farmers. According to CAGE 16% of male nonfarmers versus 11 % of farmers (p<0,032) had alcohol problems. There was no difference for females. Male farmers less commonly sought medical attention than non-farmers for anxiety, alcoholism and drug abuse. Farmers more often felt that their work was challenging in a positive way and also that work tasks were too complicated. CONCLUSIONS: Mental health disturbances were less common in animal farmers. Educating farmers on work related issues might be important in improving the farming environment.

[Occupational accidents in Icelandic farmers. Risk factor analysis using questionnaire]. / Vinnuslys íklendra baenda. Mat á áhaettutháttum med spurniningalista.

BACKGROUND: There is limited information on occupational injuries among Icelandic farmers. It has been suggested that they are common. This is thought to be in part because of the unique work environment of farmers. The aims of the study were to study occupational accidents among farmers and their effects on absence from work, doctor visits and well-being. METHODS: A cross sectional study of all animal farmers in Iceland operating running a farm of more than 100 animal (sheep) units. A total of 2042 farmers were sent a detailed questionnaire concerning general health symptoms, occupational injuries and doctor visits (response rate 54%). RESULTS: Occupational accidents were common among middle aged and older farmers and lead often to prolonged absence from work. Livestock was most common cause of the accidents, while the association with using alcohol while working was clear. Those involved in occupational accidents more commonly visited a doctor for musculoskeletal symptoms and pain. They also estimated physical and mental well-being worse and had more psychiatric symptoms. CONCLUSIONS: Occupational accidents were common among farmers and lead to prolonged absence from work. They lead to more doctor visits and and worse wellbeing. These results can be used to reinforce health care and preventive measures against occupational accidents among farmers.

[General health in Icelandic farmers]. / Almennt heilsufar íslenskra baenda.

BACKGROUND: There is a limited information on the general health of Icelandic farmers. It has been suggested that it might be worse than among other professions. This is thought to be in part because of the unique work environment of farmers.The aims of the study were to compare the general health of animal farmers with a group of non-farmers, and test the hypothesis that animal farmers overall have a better general health than non-farmers. METHODS: A cross sectional study of all animal farmers in Iceland operating running a farm of more than 100 animal (sheep) units compared with a group of non-farmers. A total of 2042 farmers were sent a detailed questionnaire concerning general health symptoms and doctor visits (response rate 54%). The comparison group consisted of 1500 randomly chosen non-farming individuals (response rate 46%). RESULTS: Farmers comprised more males, were older and smoked less than non-farmers. When general health symptoms for the last 12 months were compared between farmers and non-farmers, minor differences were noted. Farmers less commonly had restless legs, fatigue, diarrhea, allergy and hearing loss. There were no differences in doctor visits for many chronic diseases such as diabetes and hypertension despite the age difference between the groups. Repeated absence from work was less common among farmers and they had shorter sick leaves than comparison group. CONCLUSIONS: Minor differences were noted in general symptoms and doctor visits between farmers and non-farmers despite the fact that farmers were older. Absence from work for illness is less common among farmers. This study suggest that farmers general health is not worse than that of others.

[House dust mites at Icelandic farms]. / Maurar í húsryki á íslenskum bóndabaejum.

BACKGROUND: Sensitization to Dermatophagoides pteronyssinus (D. pteronyssinus) occurs in 9% of the Reykjavik population, despite the fact that no Der p 1 antigen has been found in the area. A recent study revealed that sensitized persons more often had a childhood history of work or holiday stay in rural areas than controls. As a follow up we studied the risk of exposure to mites in farmland dwellings. METHODS: In a survey of work-related lung disorders among farmers in the south and west of Iceland, 80 samples of house dust, representing 42 farms, were collected from bedroom mattresses and the floors in living rooms and examined for mites. Treatment of samples was identical with the method used earlier in the Reykjavik investigation (ECRHS II). RESULTS: In contrast to the Reykjavik results, dust from farm dwellings showed a large diversity of mites. Seventeen taxons were found, with Acarus siro and D. pteronyssinus in 13 and 8 farms respectively, but the samples did not show signs that any of the taxons actually had lived or reproduced where they were collected. CONCLUSION: The finding of D. pteronyssinus in farmland dwellings provides a possible explanation of why some Reykjavik citizens might have developed sensitization to this mite, even though cross sensitization to other species of mites could give a false positive reaction to D. pteronyssinus in at least some of those cases. Our observations did not support the idea that the mites were living in the dwellings and an explanation for their occurrence must be sought in the outdoor environment.