(Latin) In mythology, the personification of night
Noxi, Noxia, Noxea, Noxy, Noxey, Noxie, Noxee
Noxi, Noxia, Noxea, Noxy, Noxey, Noxie, Noxee
Scientists have engineered appropriate genes from other organisms into BACTERIA, or sometimes plants, to accelerate this natural evolutionary process. For e?ective ‘digestion of waste’, a micro-organism must quickly and completely digest organic waste without producing unpleasant smells or noxious gases, be non-pathogenic and be able to reproduce in hostile conditions. For example, American researchers have discovered an anaerobic bacterium that neutralises dangerous chlorinated chemical compounds such as trichlorethane, which can pollute soil, into a harmless molecule called ethens. But the bacteria do not thrive in soil. So the dechlorinating genes in this bacterium are transferred to bacteria that are acclimatised to living in toxic areas and can more e?ciently carry out the required detoxi?cation. Other research has been aimed at detoxifying the byproducts of DDT, a troublesome and resistant pollutant. Bioremediation should prove to be an environmentally friendly and cost-e?ective alternative to waste incineration or chemically based processes for washing contaminated soils.... bioremediation
Decubitus ulcer Also known as pressure or bed sore. Occurs when there is constant pressure on and inadequate oxygenation of an area of skin, usually overlying a bony protuberance. Elderly or in?rm people, or individuals with debilitating, emaciating or neurological illnesses, are vulnerable to the condition. Long-term pressure from a bed, wheelchair, cast or splint is the usual cause. Loss of skin sensation is a contributory factor, and muscle and bone as well as skin may be affected.
Treatment The most important treatment is prevention, keeping the patient’s back, buttocks, heels and other pressure-points clean and dry, and regularly changing his or her position. If ulcers do develop, repeated local DEBRIDEMENT, protective dressings and (in serious cases) surgical treatment are required, accompanied by an appropriate antibiotic if infection is persistent.
Venous ulcer This occurs on the lower leg or ankle and is caused by chronic HYPERTENSION in the deep leg VEINS, usually the consequences of previous deep vein thrombosis (DVT) – see THROMBOSIS; VEINS, DISEASES OF – which has destroyed the valvular system in the vein(s). The ulcer is usually preceded by chronic OEDEMA, often local eczema (see DERMATITIS), and bleeding into the skin that produces brown staining. Varicose veins may or may not be present. Control of the oedema by compression and encouragement to walk is central to management.... ulcer
In necrosis due to tuberculosis, the dead tissue is soft, dry, and cheese-like. Fatty tissue beneath the skin that has died as a result of damage or infection develops into tough scar tissue that may form a firm nodule.... necrosis
Form The liver is divided into four lobes, the greatest part being the right lobe, with a small left lobe, while the quadrate and caudate lobes are two small divisions on the back and undersurface. Around the middle of the undersurface, towards the back, a transverse ?ssure (the porta hepatis) is placed, by which the hepatic artery and portal vein carry blood into the liver, and the right and left hepatic ducts emerge, carrying o? the BILE formed in the liver to the GALL-BLADDER attached under the right lobe, where it is stored.
Position Occupying the right-hand upper part of the abdominal cavity, the liver is separated from the right lung by the DIAPHRAGM and the pleural membrane (see PLEURA). It rests on various abdominal organs, chie?y the right of the two KIDNEYS, the suprarenal gland (see ADRENAL GLANDS), the large INTESTINE, the DUODENUM and the STOMACH.
Vessels The blood supply di?ers from that of the rest of the body, in that the blood collected from the stomach and bowels into the PORTAL VEIN does not pass directly to the heart, but is ?rst distributed to the liver, where it breaks up into capillary vessels. As a result, some harmful substances are ?ltered from the bloodstream and destroyed, while various constituents of the food are stored in the liver for use in the body’s metabolic processes. The liver also receives the large hepatic artery from the coeliac axis. After circulating through capillaries, the blood from both sources is collected into the hepatic veins, which pass directly from the back surface of the liver into the inferior vena cava.
Minute structure The liver is enveloped in a capsule of ?brous tissue – Glisson’s capsule – from which strands run along the vessels and penetrate deep into the organ, binding it together. Subdivisions of the hepatic artery, portal vein, and bile duct lie alongside each other, ?nally forming the interlobular vessels,
which lie between the lobules of which the whole gland is built up. Each is about the size of a pin’s head and forms a complete secreting unit; the liver is built up of hundreds of thousands of such lobules. These contain small vessels, capillaries, or sinusoids, lined with stellate KUPFFER CELLS, which run into the centre of the lobule, where they empty into a small central vein. These lobular veins ultimately empty into the hepatic veins. Between these capillaries lie rows of large liver cells in which metabolic activity occurs. Fine bile capillaries collect the bile from the cells and discharge it into the bile ducts lying along the margins of the lobules. Liver cells are among the largest in the body, each containing one or two large round nuclei. The cells frequently contain droplets of fat or granules of GLYCOGEN – that is, animal starch.
Functions The liver is, in e?ect, a large chemical factory and the heat this produces contributes to the general warming of the body. The liver secretes bile, the chief constituents of which are the bile salts (sodium glycocholate and taurocholate), the bile pigments (BILIRUBIN and biliverdin), CHOLESTEROL, and LECITHIN. These bile salts are collected and formed in the liver and are eventually converted into the bile acids. The bile pigments are the iron-free and globin-free remnant of HAEMOGLOBIN, formed in the Kup?er cells of the liver. (They can also be formed in the spleen, lymph glands, bone marrow and connective tissues.) Bile therefore serves several purposes: it excretes pigment, the breakdown products of old red blood cells; the bile salts increase fat absorption and activate pancreatic lipase, thus aiding the digestion of fat; and bile is also necessary for the absorption of vitamins D and E.
The other important functions of the liver are as follows:
In the EMBRYO it forms red blood cells, while the adult liver stores vitamin B12, necessary for the proper functioning of the bone marrow in the manufacture of red cells.
It manufactures FIBRINOGEN, ALBUMINS and GLOBULIN from the blood.
It stores IRON and copper, necessary for the manufacture of red cells.
It produces HEPARIN, and – with the aid of vitamin K – PROTHROMBIN.
Its Kup?er cells form an important part of the RETICULO-ENDOTHELIAL SYSTEM, which breaks down red cells and probably manufactures ANTIBODIES.
Noxious products made in the intestine and absorbed into the blood are detoxicated in the liver.
It stores carbohydrate in the form of glycogen, maintaining a two-way process: glucose
glycogen.
CAROTENE, a plant pigment, is converted to vitamin A, and B vitamins are stored.
It splits up AMINO ACIDS and manufactures UREA and uric acids.
It plays an essential role in the storage and metabolism of FAT.... liver
Occupational health includes both mental and physical health. It is about compliance with health-and-safety-at-work legislation (and common law duties) and about best practice in providing work environments that reduce risks to health and safety to lowest practicable levels. It includes workers’ ?tness to work, as well as the management of the work environment to accommodate people with disabilities, and procedures to facilitate the return to work of those absent with long-term illness. Occupational health incorporates several professional groups, including occupational physicians, occupational health nurses, occupational hygienists, ergonomists, disability managers, workplace counsellors, health-and-safety practitioners, and workplace physiotherapists.
In the UK, two key statutes provide a framework for occupational health: the Health and Safety at Work, etc. Act 1974 (HSW Act); and the Disability Discrimination Act 1995 (DDA). The HSW Act states that employers have a duty to protect the health, safety and welfare of their employees and to conduct their business in a way that does not expose others to risks to their health and safety. Employees and self-employed people also have duties under the Act. Modern health-and-safety legislation focuses on assessing and controlling risk rather than prescribing speci?c actions in di?erent industrial settings. Various regulations made under the HSW Act, such as the Control of Substances Hazardous to Health Regulations, the Manual Handling Operations Regulations and the Noise at Work Regulations, set out duties with regard to di?erent risks, but apply to all employers and follow the general principles of risk assessment and control. Risks should be controlled principally by removing or reducing the hazard at source (for example, by substituting chemicals with safer alternatives, replacing noisy machinery, or automating tasks to avoid heavy lifting). Personal protective equipment, such as gloves and ear defenders, should be seen as a last line of defence after other control measures have been put in place.
The employment provisions of the DDA require employers to avoid discriminatory practice towards disabled people and to make reasonable adjustments to working arrangements where a disabled person is placed at a substantial disadvantage to a non-disabled person. Although the DDA does not require employers to provide access to rehabilitation services – even for those injured or made ill at work – occupational-health practitioners may become involved in programmes to help people get back to work after injury or long-term illness, and many businesses see the retention of valuable sta? as an attractive alternative to medical retirement or dismissal on health grounds.
Although a major part of occupational-health practice is concerned with statutory compliance, the workplace is also an important venue for health promotion. Many working people rarely see their general practitioner and, even when they do, there is little time to discuss wider health issues. Occupational-health advisers can ?ll in this gap by providing, for example, workplace initiatives on stopping smoking, cardiovascular health, diet and self-examination for breast and testicular cancers. Such initiatives are encouraged because of the perceived bene?ts to sta?, to the employing organisation and to the wider public-health agenda. Occupational psychologists recognise the need for the working population to achieve a ‘work-life balance’ and the promotion of this is an increasing part of occupational health strategies.
The law requires employers to consult with their sta? on health-and-safety matters. However, there is also a growing understanding that successful occupational-health management involves workers directly in the identi?cation of risks and in developing solutions in the workplace. Trade unions play an active role in promoting occupational health through local and national campaigns and by training and advising elected workplace safety representatives.
Occupational medicine The branch of medicine that deals with the control, prevention, diagnosis, treatment and management of ill-health and injuries caused or made worse by work, and with ensuring that workers are ?t for the work they do.
Occupational medicine includes: statutory surveillance of workers’ exposure to hazardous agents; advice to employers and employees on eliminating or reducing risks to health and safety at work; diagnosis and treatment/management of occupational illness; advice on adapting the working environment to suit the worker, particularly those with disabilities or long-term health problems; and advice on the return to work and, if necessary, rehabilitation of workers absent through illness. Occupational physicians may play a wider role in monitoring the health of workplace populations and in advising employers on controlling health hazards where ill-health trends are observed. They may also conduct epidemiological research (see EPIDEMIOLOGY) on workplace diseases.
Because of the occupational physician’s dual role as adviser to both employer and employee, he or she is required to be particularly diligent with regards to the individual worker’s medical CONFIDENTIALITY. Occupational physicians need to recognise in any given situation the context they are working in, and to make sure that all parties are aware of this.
Occupational medicine is a medical discipline and thus is only part of the broader ?eld of occupational health. Although there are some speci?c clinical duties associated with occupational medicine, such as diagnosis of occupational disease and medical screening, occupational physicians are frequently part of a multidisciplinary team that might include, for example, occupational-health nurses, healthand-safety advisers, ergonomists, counsellors and hygienists. Occupational physicians are medical practitioners with a post-registration quali?cation in occupational medicine. They will have completed a period of supervised in-post training. In the UK, the Faculty of Occupational Medicine of the Royal College of Physicians has three categories of membership, depending on quali?cations and experience: associateship (AFOM); membership (MFOM); and fellowship (FFOM).
Occupational diseases Occupational diseases are illnesses that are caused or made worse by work. In their widest sense, they include physical and mental ill-health conditions.
In diagnosing an occupational disease, the clinician will need to examine not just the signs and symptoms of ill-health, but also the occupational history of the patient. This is important not only in discovering the cause, or causes, of the disease (work may be one of a number of factors), but also in making recommendations on how the work should be modi?ed to prevent a recurrence – or, if necessary, in deciding whether or not the worker is able to return to that type of work. The occupational history will help in deciding whether or not other workers are also at risk of developing the condition. It will include information on:
the nature of the work.
how the tasks are performed in practice.
the likelihood of exposure to hazardous agents (physical, chemical, biological and psychosocial).
what control measures are in place and the extent to which these are adhered to.
previous occupational and non-occupational exposures.
whether or not others have reported similar symptoms in relation to the work. Some conditions – certain skin conditions,
for example – may show a close relationship to work, with symptoms appearing directly only after exposure to particular agents or possibly disappearing at weekends or with time away from work. Others, however, may be chronic and can have serious long-term implications for a person’s future health and employment.
Statistical information on the prevalence of occupational disease in the UK comes from a variety of sources, including o?cial ?gures from the Industrial Injuries Scheme (see below) and statutory reporting of occupational disease (also below). Neither of these o?cial schemes provides a representative picture, because the former is restricted to certain prescribed conditions and occupations, and the latter suffers from gross under-reporting. More useful are data from the various schemes that make up the Occupational Diseases Intelligence Network (ODIN) and from the Labour Force Survey (LFS). ODIN data is generated by the systematic reporting of work-related conditions by clinicians and includes several schemes. Under one scheme, more than 80 per cent of all reported diseases by occupational-health physicians fall into just six of the 42 clinical disease categories: upper-limb disorders; anxiety, depression and stress disorders; contact DERMATITIS; lower-back problems; hearing loss (see DEAFNESS); and ASTHMA. Information from the LFS yields a similar pattern in terms of disease frequency. Its most recent survey found that over 2 million people believed that, in the previous 12 months, they had suffered from an illness caused or made worse by work and that
19.5 million working days were lost as a result. The ten most frequently reported disease categories were:
stress and mental ill-health (see MENTAL ILLNESS): 515,000 cases.
back injuries: 508,000.
upper-limb and neck disorders: 375,000.
lower respiratory disease: 202,000.
deafness, TINNITUS or other ear conditions: 170,000.
lower-limb musculoskeletal conditions: 100,000.
skin disease: 66,000.
headache or ‘eyestrain’: 50,000.
traumatic injury (includes wounds and fractures from violent attacks at work): 34,000.
vibration white ?nger (hand-arm vibration syndrome): 36,000. A person who develops a chronic occu
pational disease may be able to sue his or her employer for damages if it can be shown that the employer was negligent in failing to take reasonable care of its employees, or had failed to provide a system of work that would have prevented harmful exposure to a known health hazard. There have been numerous successful claims (either awarded in court, or settled out of court) for damages for back and other musculoskeletal injuries, hand-arm vibration syndrome, noise-induced deafness, asthma, dermatitis, MESOTHELIOMA and ASBESTOSIS. Employers’ liability (workers’ compensation) insurers are predicting that the biggest future rise in damages claims will be for stress-related illness. In a recent study, funded by the Health and Safety Executive, about 20 per cent of all workers – more than 5 million people in the UK – claimed to be ‘very’ or ‘extremely’ stressed at work – a statistic that is likely to have a major impact on the long-term health of the working population.
While victims of occupational disease have the right to sue their employers for damages, many countries also operate a system of no-fault compensation for the victims of prescribed occupational diseases. In the UK, more than 60 diseases are prescribed under the Industrial Injuries Scheme and a person will automatically be entitled to state compensation for disability connected to one of these conditions, provided that he or she works in one of the occupations for which they are prescribed. The following short list gives an indication of the types of diseases and occupations prescribed under the scheme:
CARPAL TUNNEL SYNDROME connected to the use of hand-held vibrating tools.
hearing loss from (amongst others) use of pneumatic percussive tools and chainsaws, working in the vicinity of textile manufacturing or woodworking machines, and work in ships’ engine rooms.
LEPTOSPIROSIS – infection with Leptospira (various listed occupations).
viral HEPATITIS from contact with human blood, blood products or other sources of viral hepatitis.
LEAD POISONING, from any occupation causing exposure to fumes, dust and vapour from lead or lead products.
asthma caused by exposure to, among other listed substances, isocyanates, curing agents, solder ?ux fumes and insects reared for research.
mesothelioma from exposure to asbestos.
In the UK, employers and the self-employed have a duty to report all occupational injuries (if the employee is o? work for three days or more as a result), diseases or dangerous incidents to the relevant enforcing authority (the Health and Safety Executive or local-authority environmental-health department) under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995 (RIDDOR). Despite this statutory duty, comparatively few diseases are reported so that ?gures generated from RIDDOR reports do not give a useful indication of the scale of occupational diseases in the UK. The statutory reporting of injuries is much better, presumably because of the clear and acute relationship between a workplace accident and the resultant injury. More than 160,000 injuries are reported under RIDDOR every year compared with just 2,500 or so occupational diseases, a gross underestimate of the true ?gure.
There are no precise ?gures for the number of people who die prematurely because of work-related ill-health, and it would be impossible to gauge the exact contribution that work has on, for example, cardiovascular disease and cancers where the causes are multifactorial. The toll would, however, dwarf the number of deaths caused by accidents at work. Around 250 people are killed by accidents at work in the UK each year – mesothelioma, from exposure to asbestos at work, alone kills more than 1,300 people annually.
The following is a sample list of occupational diseases, with brief descriptions of their aetiologies.
Inhaled materials
PNEUMOCONIOSIS covers a group of diseases which cause ?brotic lung disease following the inhalation of dust. Around 250–300 new cases receive bene?t each year – mostly due to coal dust with or without silica contamination. SILICOSIS is the more severe disease. The contraction in the size of the coal-mining industry as well as improved dust suppression in the mines have diminished the importance of this disease, whereas asbestos-related diseases now exceed 1,000 per year. Asbestos ?bres cause a restrictive lung disease but also are responsible for certain malignant conditions such as pleural and peritoneal mesothelioma and lung cancer. The lung-cancer risk is exacerbated by cigarette-smoking.
Even though the use of asbestos is virtually banned in the UK, many workers remain at risk of exposure because of the vast quantities present in buildings (much of which is not listed in building plans). Carpenters, electricians, plumbers, builders and demolition workers are all liable to exposure from work that disturbs existing asbestos. OCCUPATIONAL ASTHMA is of increasing importance – not only because of the recognition of new allergic agents (see ALLERGY), but also in the number of reported cases. The following eight substances are most frequently linked to occupational asthma (key occupations in brackets): isocyanates (spray painters, electrical processors); ?our and grain (bakers and farmers); wood dust (wood workers); glutaraldehyde (nurses, darkroom technicians); solder/colophony (welders, electronic assembly workers); laboratory animals (technicians, scientists); resins and glues (metal and electrical workers, construction, chemical processors); and latex (nurses, auxiliaries, laboratory technicians).
The disease develops after a short, symptomless period of exposure; symptoms are temporally related to work exposures and relieved by absences from work. Removal of the worker from exposure does not necessarily lead to complete cessation of symptoms. For many agents, there is no relationship with a previous history of ATOPY. Occupational asthma accounts for about 10 per cent of all asthma cases. DERMATITIS The risk of dermatitis caused by an allergic or irritant reaction to substances used or handled at work is present in a wide variety of jobs. About three-quarters of cases are irritant contact dermatitis due to such agents as acids, alkalis and solvents. Allergic contact dermatitis is a more speci?c response by susceptible individuals to a range of allergens (see ALLERGEN). The main occupational contact allergens include chromates, nickel, epoxy resins, rubber additives, germicidal agents, dyes, topical anaesthetics and antibiotics as well as certain plants and woods. Latex gloves are a particular cause of occupational dermatitis among health-care and laboratory sta? and have resulted in many workers being forced to leave their profession through ill-health. (See also SKIN, DISEASES OF.)
Musculoskeletal disorders Musculoskeletal injuries are by far the most common conditions related to work (see LFS ?gures, above) and the biggest cause of disability. Although not all work-related, musculoskeletal disorders account for 36.5 per cent of all disabilities among working-age people (compared with less than 4 per cent for sight and hearing impairment). Back pain (all causes – see BACKACHE) has been estimated to cause more than 50 million days lost every year in sickness absence and costs the UK economy up to £5 billion annually as a result of incapacity or disability. Back pain is a particular problem in the health-care sector because of the risk of injury from lifting and moving patients. While the emphasis should be on preventing injuries from occurring, it is now well established that the best way to manage most lower-back injuries is to encourage the patient to continue as normally as possible and to remain at work, or to return as soon as possible even if the patient has some residual back pain. Those who remain o? work on long-term sick leave are far less likely ever to return to work.
Aside from back injuries, there are a whole range of conditions affecting the upper limbs, neck and lower limbs. Some have clear aetiologies and clinical signs, while others are less well de?ned and have multiple causation. Some conditions, such as carpal tunnel syndrome, are prescribed diseases in certain occupations; however, they are not always caused by work (pregnant and older women are more likely to report carpal tunnel syndrome irrespective of work) and clinicians need to be careful when assigning work as the cause without ?rst considering the evidence. Other conditions may be revealed or made worse by work – such as OSTEOARTHRITIS in the hand. Much attention has focused on injuries caused by repeated movement, excessive force, and awkward postures and these include tenosynovitis (in?ammation of a tendon) and epicondylitis. The greatest controversy surrounds upper-limb disorders that do not present obvious tissue or nerve damage but nevertheless give signi?cant pain and discomfort to the individual. These are sometimes referred to as ‘repetitive strain injury’ or ‘di?use RSI’. The diagnosis of such conditions is controversial, making it di?cult for sufferers to pursue claims for compensation through the courts. Psychosocial factors, such as high demands of the job, lack of control and poor social support at work, have been implicated in the development of many upper-limb disorders, and in prevention and management it is important to deal with the psychological as well as the physical risk factors. Occupations known to be at particular risk of work-related upper-limb disorders include poultry processors, packers, electronic assembly workers, data processors, supermarket check-out operators and telephonists. These jobs often contain a number of the relevant exposures of dynamic load, static load, a full or excessive range of movements and awkward postures. (See UPPER LIMB DISORDERS.)
Physical agents A number of physical agents cause occupational ill-health of which the most important is occupational deafness. Workplace noise exposures in excess of 85 decibels for a working day are likely to cause damage to hearing which is initially restricted to the vital frequencies associated with speech – around 3–4 kHz. Protection from such noise is imperative as hearing aids do nothing to ameliorate the neural damage once it has occurred.
Hand-arm vibration syndrome is a disorder of the vascular and/or neural endings in the hands leading to episodic blanching (‘white ?nger’) and numbness which is exacerbated by low temperature. The condition, which is caused by vibrating tools such as chain saws and pneumatic hammers, is akin to RAYNAUD’S DISEASE and can be disabling.
Decompression sickness is caused by a rapid change in ambient pressure and is a disease associated with deep-sea divers, tunnel workers and high-?ying aviators. Apart from the direct effects of pressure change such as ruptured tympanic membrane or sinus pain, the more serious damage is indirectly due to nitrogen bubbles appearing in the blood and blocking small vessels. Central and peripheral nervous-system damage and bone necrosis are the most dangerous sequelae.
Radiation Non-ionising radiation from lasers or microwaves can cause severe localised heating leading to tissue damage of which cataracts (see under EYE, DISORDERS OF) are a particular variety. Ionising radiation from radioactive sources can cause similar acute tissue damage to the eyes as well as cell damage to rapidly dividing cells in the gut and bone marrow. Longer-term effects include genetic damage and various malignant disorders of which LEUKAEMIA and aplastic ANAEMIA are notable. Particular radioactive isotopes may destroy or induce malignant change in target organs, for example, 131I (thyroid), 90Sr (bone). Outdoor workers may also be at risk of sunburn and skin cancers. OTHER OCCUPATIONAL CANCERS Occupation is directly responsible for about 5 per cent of all cancers and contributes to a further 5 per cent. Apart from the cancers caused by asbestos and ionising radiation, a number of other occupational exposures can cause human cancer. The International Agency for Research on Cancer regularly reviews the evidence for carcinogenicity of compounds and industrial processes, and its published list of carcinogens is widely accepted as the current state of knowledge. More than 50 agents and processes are listed as class 1 carcinogens. Important occupational carcinogens include asbestos (mesothelioma, lung cancer); polynuclear aromatic hydrocarbons such as mineral oils, soots, tars (skin and lung cancer); the aromatic amines in dyestu?s (bladder cancer); certain hexavalent chromates, arsenic and nickel re?ning (lung cancer); wood and leather dust (nasal sinus cancer); benzene (leukaemia); and vinyl chloride monomer (angiosarcoma of the liver). It has been estimated that elimination of all known occupational carcinogens, if possible, would lead to an annual saving of 5,000 premature deaths in Britain.
Infections Two broad categories of job carry an occupational risk. These are workers in contact with animals (farmers, veterinary surgeons and slaughtermen) and those in contact with human sources of infection (health-care sta? and sewage workers).
Occupational infections include various zoonoses (pathogens transmissible from animals to humans), such as ANTHRAX, Borrelia burgdorferi (LYME DISEASE), bovine TUBERCULOSIS, BRUCELLOSIS, Chlamydia psittaci, leptospirosis, ORF virus, Q fever, RINGWORM and Streptococcus suis. Human pathogens that may be transmissible at work include tuberculosis, and blood-borne pathogens such as viral hepatitis (B and C) and HIV (see AIDS/HIV). Health-care workers at risk of exposure to infected blood and body ?uids should be immunised against hapatitis B.
Poisoning The incidence of occupational poisonings has diminished with the substitution of noxious chemicals with safer alternatives, and with the advent of improved containment. However, poisonings owing to accidents at work are still reported, sometimes with fatal consequences. Workers involved in the application of pesticides are particularly at risk if safe procedures are not followed or if equipment is faulty. Exposure to organophosphate pesticides, for example, can lead to breathing diffculties, vomiting, diarrhoea and abdominal cramps, and to other neurological effects including confusion and dizziness. Severe poisonings can lead to death. Exposure can be through ingestion, inhalation and dermal (skin) contact.
Stress and mental health Stress is an adverse reaction to excessive pressures or demands and, in occupational-health terms, is di?erent from the motivational impact often associated with challenging work (some refer to this as ‘positive stress’). Stress at work is often linked to increasing demands on workers, although coping can often prevent the development of stress. The causes of occupational stress are multivariate and encompass job characteristics (e.g. long or unsocial working hours, high work demands, imbalance between e?ort and reward, poorly managed organisational change, lack of control over work, poor social support at work, fear of redundancy and bullying), as well as individual factors (such as personality type, personal circumstances, coping strategies, and availability of psychosocial support outside work). Stress may in?uence behaviours such as smoking, alcohol consumption, sleep and diet, which may in turn affect people’s health. Stress may also have direct effects on the immune system (see IMMUNITY) and lead to a decline in health. Stress may also alter the course and response to treatment of conditions such as cardiovascular disease. As well as these general effects of stress, speci?c types of disorder may be observed.
Exposure to extremely traumatic incidents at work – such as dealing with a major accident involving multiple loss of life and serious injury
(e.g. paramedics at the scene of an explosion or rail crash) – may result in a chronic condition known as post-traumatic stress disorder (PTSD). PTSD is an abnormal psychological reaction to a traumatic event and is characterised by extreme psychological discomfort, such as anxiety or panic when reminded of the causative event; sufferers may be plagued with uncontrollable memories and can feel as if they are going through the trauma again. PTSD is a clinically de?ned condition in terms of its symptoms and causes and should not be used to include normal short-term reactions to trauma.... occupational health, medicine and diseases
Structure
CORIUM The foundation layer. It overlies the subcutaneous fat and varies in thickness from 0·5–3.0 mm. Many nerves run through the corium: these have key roles in the sensations of touch, pain and temperature (see NEURON(E)). Blood vessels nourish the skin and are primarily responsible for regulating the body temperature. Hairs are bedded in the corium, piercing the epidermis (see below) to cover the skin in varying amounts in di?erent parts of the body. The sweat glands are also in the corium and their ducts lead to the surface. The ?brous tissue of the corium comprises interlocking white ?brous elastic bundles. The corium contains many folds, especially over joints and on the palms of hands and soles of feet with the epidermis following the contours. These are permanent throughout life and provide unique ?ngerprinting identi?cation. HAIR Each one has a root and shaft, and its varying tone originates from pigment scattered throughout it. Bundles of smooth muscle (arrectores pilorum) are attached to the root and on contraction cause the hair to stand vertical. GLANDS These occur in great numbers in the skin. SEBACEOUS GLANDS secrete a fatty substance and sweat glands a clear watery ?uid (see PERSPIRATION). The former are made up of a bunch of small sacs producing fatty material that reaches the surface via the hair follicle. Around three million sweat or sudoriparous glands occur all over the body surface; sited below the sebaceous glands they are unconnected to the hairs. EPIDERMIS This forms the outer layer of skin and is the cellular layer covering the body surface: it has no blood vessels and its thickness varies from 1 mm on the palms and soles to 0·1 mm on the face. Its outer, impervious, horny layer comprises several thicknesses of ?at cells (pierced only by hairs and sweat-gland openings) that are constantly rubbed o? as small white scales; they are replaced by growing cells from below. The next, clear layer forms a type of membrane below which the granular stratum cells are changing from their origins as keratinocytes in the germinative zone, where ?ne sensory nerves also terminate. The basal layer of the germinative zone contains melanocytes which produce the pigment MELANIN, the cause of skin tanning.
Nail A modi?cation of skin, being analagous to the horny layer, but its cells are harder and more adherent. Under the horny nail is the nail bed, comprising the well-vascularised corium (see above) and the germinative zone. Growth occurs at the nail root at a rate of around 0·5 mm a week – a rate that increases in later years of life.
Skin functions By its ability to control sweating and open or close dermal blood vessels, the skin plays a crucial role in maintaining a constant body temperature. Its toughness protects the body from mechanical injury. The epidermis is a two-way barrier: it prevents the entry of noxious chemicals and microbes, and prevents the loss of body contents, especially water, electrolytes and proteins. It restricts electrical conductivity and to a limited extent protects against ultraviolet radiation.
The Langerhans’ cells in the epidermis are the outposts of the immune system (see IMMUNITY), just as the sensory nerves in the skin are the outposts of the nervous system. Skin has a social function in its ability to signal emotions such as fear or anger. Lastly it has a role in the synthesis of vitamin D.... skin
Health Encyclopedia