Health Conditions Associated with
|Normal||Chemical exposures do not cause health problems|
|Sensitisation||Susceptible individuals are affected at low
exposures to chemicals.
Sometimes the mechanism of effect is allergic.
|Irritancy||Mainly non-specific or subjective signs and symptoms at chemical exposures that are considered "acceptable".||-algias
|Inflamation||More specific signs and symptoms at or above acceptable exposure to chemicals.||-itis|
|Injury||Damage and injury to unacceptable chemical exposures. Poisoning and clinical disease.||-osis|
Chronic Fatigue Syndrome
A definition was issued by the US Centers for Disease Control (CDC) in 1988.11 A more restrictive definition was issued by the US CDC in 1995 (see Figure 4).
Controversy remains about the possible physiological, biochemical, immunological, psychological and social aspects of the condition, and possibly all five are important to varying degrees in individual chronic fatigue syndrome sufferers,
Research studies have confirmed that the majority of patients with the chronic fatigue syndrome:
Psychological and immunological factors both appear to contribute to chronic fatigue syndrome (CFS). By comparing CFS with other disorders in which fatigue is a prominent symptom, the association between fatigue, psychological vulnerability, depression, and immune function can be further defined. The 1988 definition of CFS by the Centers for, Disease Control encompasses several conditions in which the major characteristic is severe fatigue associated with constitutional symptoms. Several studies have identified immune dysfunction in CFS patients, but the specificity of these findings remains unclear. Most studies have shown that CFS patients, compared with other patients with chronic medical illness, experience more disabling fatigue. Some investigators have found a higher incidence of concurrent and past psychiatric illness in CFS patients compared with other medical patients, thereby suggesting an underlying psychopathology in CFS. However, other studies have not found a higher than expected incidence of past depression in CFS patients and have further shown that many CFS patients have no identifiable psychopathology. CFS appears to be a heterogeneous entity. Although there may be a high coincidence of major depression in CFS, a substantial proportion of patients lack any identifiable psychiatric disorder yet manifest the syndrome, thereby suggesting it has an autonomous entity. Recent data from psychological, neurological, and immunological studies that address these issues indicate that despite the evolving nature of our current understanding of CFS, a rational diagnostic and therapeutic approach to CFS is possible.
|Exclude if another cause for chronic fatigue is found|
Chemically Related Chronic Fatigue Syndrome
As noted above, some of the features of multiple chemical sensitivity have similarities with chronic fatigue syndrome, such as fatigue and depression. Labelling of a set of symptoms, such as chronic fatigue syndrome or multiple chemical sensitivity is one way to get recognition that they are medical conditions. However, it is also possible to consider that where chemical exposure is concerned, these particular syndromes are at two ends of a continuum of disease.
The chemically exposed individual with debilitating fatigue may not meet all the diagnostic criteria of CFS or MCS. In some cases, they may be closer to one than the other.
Chemically related CFS is an controversial and slowly emerging medical condition, in which sufferers appear to show fairly similar characteristics:
Multiple Chemical Sensitivity
Like CFS, MCS is a real disease. The now well accepted name multiple chemical sensitivity was established in the late 1980s, when the first articles on MCS were published. Until that time, there was a lack of a clear definition as to what MCS was, as several medical specialities squabbled about whether MCS is a medical condition, and if so, how it could be diagnosed. Some of the more divisive infighting has been between the allergists and immunologists on one side and the clinical ecologists on the other. This controversy made it difficult for patients to find objective information about the issue, and impeded their ability to resolve MCS- related problems at the workplace, insurance or litigation levels.
Disease can be a pathological process, and not all persons with a disease are ill. Symptoms of illness associated with a disease may be manifest or persist after the disease has disappeared. Many factors, including personal characteristics and social circumstances, can be responsible for recovery from disease and illness. There are many different neurological and psychiatric syndromes that follow acute illness, but their clinical pictures and pathogenisis are poorly understood.
Historically, a syndrome called neurasthenia or "American nervousness" was described in 1880 which is similar to MCS. Modern attempts to deal with the "chemical susceptibility problem"" began in the 1950's, with the original work of Randolph, who proposed a model of multiple chemical sensitivity consisting of the inability of the body to adapt to chemicals and the development of responsiveness to extremely low concentrations after sensitisation in the mid 1950's. Early research investigated food intolerances.
The numbers of cases of people with such a chemical sensitivity continues to grow, and the term Multiple Chemical Sensitivity (MCS) has been used to describe this condition. Although this name is now the most often cited, this condition has been known by a variety of names such as environmental illness, hypersensitivity syndrome, twentieth century disease, total allergy syndrome and chemical sensitivity problem.
Diagnosis of MCS
Conditions in which physical symptoms are unsupported by physical findings and have diagnostic labels that describe the disorder without indicating either cause or pathology are especially troubling for the medical practitioner. However, a working definition for MCS was established in 1987. This definition, subsequently modified, suggested a grouping of effects in workers who had been exposed to low levels of several chemicals. A Symposium on MCS was held by the Association of Occupational and Environmental Clinics (AOEC) an the USA in 1991 which proposed a "research definition" for MCS for the purposes of epidemiological study:
Symptoms of MCS
As a group, people suffering from MCS have a large number and range of symptoms they associate with chemical exposures. The complaints are physical and mental and involve nearly all systems of the body. The commonest symptoms include:
This huge range of symptoms has meant that some medical practitioners have dismissed chemical sensitivity as a real medical condition because it cannot be diagnosed, preferring to suggest immunological, neurological or psychological alternatives (sometimes as a means of getting rid of the patient).
It is quite common in cases of this nature for a patient to be seen by a number of doctors and specialists, some of who are dismissive or unhelpful. However, those medical practioners who are able to see beyond the limited confines of their own fields of speciality can sometimes see more than a sick liver or a dysfunctional nervous system to see a person who needs help. Such doctors can usually provide some help to the chemically sensitive person, often providing a range of advice, including the the exposure basis of that condition, likely prognosis, and recommendations for recovery or level of incapacity.
Different types of chemical sensitive individual
There are four main types who contain individuals in which heightened reactivity to chemical exposures has been reported -
Nature of exposure
|Industrial Workers||Acute or chronic exposure to industrial chemicals.||Primarily males.
20 to 65 years old.
(in "tight buildings")
Off gassing from construction or refurbishment materials or from office equipment.
|More females than males. White
20 to 65 years old. School children.
|Contaminated communities||Toxic waste sites. Contamination by
nearby industry sites.
Aerial pesticide spraying. Groundwater contamination. Other community exposures.
|Middle to lower class. All ages,
male and female.
Children or infants affected first or most, possible effects in pregnant women.
Indoor air (domestic). Pesticides, consumer products and drugs.
|White upper to middle class, primarily females, 30-50 years old.|
Exposures that precipitate symptoms of MCS
Initially, individuals respond to one sort of chemical exposure, but if the spreading or broadening phenomenon occurs, the affected individual may respond to a much wider range of chemicals, and the exposures that precipitate symptoms become lower and lower. Table 2 shows a wide range of exposures that have been reported to provoke such symptoms in the chemically sensitive individual.
Type of Exposure
|Specific chemicals||Ammonia Bleach Formaldehyde Glutaraldehyde||Mineral Turpentine Petrol
Industrial air contaminants
Pesticides in building fumigation Photocopy toner
Sulphur residues and processing fumes Utility gas
Vapours from paints
|Domestic contaminants||Bed linen washed with detergents, or
treated with starch Chloride in water
Cleaning products, disinfectants, bleach
Food additives/contaminants, flavouring agents, preservatives, and sweetening agents
Fragrances from perfumes and toiletries
Insect sprays and repellents
Laser printer and photocopier emissions
|Medication and drugs, including
antibiotics, sulphonamides, aspirin,
Off-gases from some construction materials Plastic containers
Tobacco smoke (including passive smoking) Tar fumes (from roads and roof tar)
Vehicle exhausts (petrol and diesel)
Chronic Fatigue in MCS
Chronic fatigue is a common out- come, but that debilitating fatigue and a number of associated symptoms following a viral infection for periods greater than six months has been given the name post viral chronic fatigue syndrome. Similar types of symptoms (but with more symptoms and probably less fatigue) may also be reported by people exposed to chemicals. Fatigue, and chronic fatigue, is often part of multiple chemical sensitivity.
However, both these descriptions relate to a condition where the normal body mechanisms for dealing with exposure (either to a virus or chemicals) do not work properly, and getting well takes much longer than it would ordinarily (in some cases more than two years, if at all). Indeed, as noted above, some of the features of multiple chemical sensitivity have similarities with chronic fatigue syndrome, such as fatigue, hypersensitivity and depression. It is possible to consider that these particular syndromes are at two ends of a continuum.
The chemically exposed individual with debilitating
fatigue may not meet all the diagnostic criteria of chronic
fatigue syndrome or multiple chemical sensitivity. In some
cases they may be closer to one than the other. This makes
diagnosis (see Figure 5) and treatment problematic.
However, chemically related chronic fatigue, that is the presence of fatigue and other symptoms following chemical exposure, sits between these two descriptions.
The Phenomenon of "spreading"
Often the sensitivity to one exposure spreads to a wider range of agents. This 'spreading' or 'broadening:' phenomenon is fairly characteristic of MCS but causes problems for some treating medical practitioners, who find it difficult to believe that such a wide range of exceptionally low level exposures can induce such a wide variety of symptoms in many organ symptoms. Most diseases have a much narrower spectrum of symptoms and signs, so multiple chemical sensitivity doesn't fit into the pattern of illnesses with which medical practitioners are familiar. In many cases, diagnostic tests are not helpful in assisting diagnosis.
Phases of MCS
There are three distinct phases of MCS:
Investigations into the basis of MCS
The basis of MCS is still to be identified, although a range of hypersensitivity, immunological, psychological, neurological and toxicological mechanisms have been suggested
Possible Mechanisms for Multiple Chemical Sensitivity
Allergic Most allergic reactions have underlying immune mechanisms that have correlates which can be measured clinically. These correlates are rarely found altered (or only mildly altered) in MCS sufferers, suggesting that MCS is not mediated through allergic mechanisms.
Autosuggestion Belief that disease (and its causes) exist may be the cause of symptoms. Further, such a belief is perpetuated and rein- forced by support groups, medical advisers and the media. Unlikely possible cause as many MCS sufferers must make massive lifestyle changes against pre-existing belief systems.
Cacosomia Altered olfactory sensitivity. The smell of chemicals may produce autonomic arousal, which becomes amplified with time. Also may be seen as odour mediated panic attacks
This theory suggests that smelling the chemical causes a behavioural response which produces the symptoms. However, the reverse in usually the case - most MCS sufferers recognise symptoms first and then find they have been exposed.
Changes in immunological measures are sometimes found in MCS sufferers, but these are often not clinically significant and are not consistent in all MCS sufferers. The changes are also sometimes linked to post viral episodes, such as viral infections.
Impairment of biochemical pathways involved in energy production Suggests that the fatigue seen in MCS (and CFS) sufferers may be due to impairment of basal energy metabolism in all cells. Those body systems with high-energy demands (such as muscles and the nervous system) are affected first.
Limbic kindling The limbic system is part of the deeper structures of the central nervous system, known to be associated with some of the more stronger emotions. Low level stimuli which do not initially produce a response and which eventually produce strong responses could be mediated through increasing activity in the limbic system. A theory that may explain the multi-organ nature of MCS, and time dependent increases in sensitivity.
Psychosomatic condition That symptoms are of psychological origin. Unlikely as most symptoms are related to the conventional toxicity of the chemicals, but at a much lower concentration.
Malingering Symptoms of MCS are produced so that sufferers can get out of work or to receive compensation. Most unlikely - the range of symptoms between sufferers is too consistent to be based on random symptoms used by many individuals for the purposeful avoidance of work.
Neurological Inflammation (in upper respiratory tract infection) It is known that respiratory tract infections produce biochemicals (such as cytokines and messenger peptides) which can cause sensitisation of nervous cells located in the respiratory system. Suggests a possible mechanism of site specific nervous system sensitisation.
Overload of biotransformation pathways (also linked with free radical production) The functional reserves in biotransformation capacity varies from individual to individual. If this reserve is close to saturation or if it is depleted, the body cannot deal with further toxic exposures. Most MCS sufferers have some disruption in bio- transformation processes (although not usually observed using the crude measures used clinically, for example, in liver disease). Also supports concepts of increasing sensitivity to lower concentrations and increasing numbers of chemicals.
Psychological illness Suggests that MC-S is produced as a by-product of misdiagnosed psychological disease. The possibility of psychological disease should be excluded in diagnosis of MCS. Further, most MCS sufferers --, undergoing psychological evaluation do not show psychological disease.
Sensitisation of the neurological system "Neurogenic switching" occurs where a stimulus at one site can produce a reaction at another site.
Most of these theories tend to break down into concepts involving:
Further, many of the other suggested mechanisms still suggest a chemically mediated trigger in the development or production of MCS symptoms.
However, when a chemical sensitivity occurs, the question that should be answered is not "does this effect correspond with identifiable medical conditions or pathological correlates?" or "why does no-one else seem to be affected by what do not appear to be high levels of exposure?" but more "would the symptoms have occurred if the person had not been exposed?" Subjects with the chemical exposures that precipitate symptoms of MCS suffer from a syndrome of disability from which they may never recover from adequately and, because of a temporal relationship between exposure and effect, are legitimate cases to consider as chemically associated.
Chris Winder is Associate Professor in the Department of Safe Science at the University of New South Wales,
Phone 02 9385 4144, fax 02 9385 6190
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