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Extract from «The Medical Perspective on Environmental Sensitivities»

by Margaret E. Sears (M.Ing., Ph.D.) Mai 2007




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Diagnostic criteria are used by physicians to identify a health condition in individuals, and by researchers to determine the proportion of the population experiencing the condition severely enough to seek medical care. Some people with environmental sensitivities are less severely affected and may not seek care. This proportion of individuals in the population is generally investigated with more general questions about reactions to perfumes or other everyday chemicals.

In January 2007, Statistics Canada reported that 5% of Canadians (1.2 million people) suffer “medically unexplained physical symptoms,” including multiple chemical sensitivity, fibromyalgia and chronic pain.(9)

According to Statistics Canada’s 2003 National Population Health Survey (N=135,573),b the prevalence of doctor-diagnosed multiple chemical sensitivities was 2.4% in people aged twelve or older,(9) and 2.9% in people thirty years of age or older.(10) The 2005 National Survey of the Work and Health of Nurses revealed that 3.6% of all Canadian nurses experienced chemical sensitivities (N=18,676).(11) Prevalence in the general American population has been reported to range from 3.1% doctor-diagnosed multiple chemical sensitivity in Atlanta, Georgia (N=1,582)12 to 6.3% doctor-diagnosed chemical sensitivity in a large California survey (N=4,046).(13)
Many more people experience less severe sensitivities. Self-reports of heightened sensitivity (feeling ill) on exposure to “everyday ” chemicals in American populations ranges from 11% of 1,057 participants in a US national survey 14 and 16% in California,(13) to 33% in rural North Carolina.(15) It is unclear to what extent people experiencing less severe intolerances are at an increased risk of developing full-blown, debilitating environmental sensitivities. However, recent studies have revealed genetic links to sensitivities,(16-22) and biochemical differences between people with sensitivities and “control” populations.(23) Clinical experience shows that increasing chemical exposures are associated with increasing symptoms and reports of sensitivity spreading to more incitants.(3,24)

More women than men are affected by environmental sensitivities. Almost twice as many women as men experienced “sick building syndrome” in a German study,(25) and approximately 60-80% of people diagnosed with environmental sensitivities in various surveys are female. (5,12,26-30)

Environmental sensitivities affect all socio-economic classes, according to population-based surveys.(12,29,30) The recent Canadian analysis indicates that people from a lower socio-economic class are more likely to report medically unexplained symptoms than are people from the highest socio-economic class.(9) On the other hand, clinic-based and citizens’ groups surveys indicate that more highly educated or affluent people with sensitivities tend to seek medical care or self-help.(5,27,28)

Sensitivities may occur in anyone, even at an early age.(31,32) Children’s respiratory, learning and behavioural difficulties may be associated with toxins passed on from the mother, as well as a variety of factors including pesticide exposure, indoor air quality and foods.(13,33-39) Studies have revealed that the prevalence of environmental sensitivities increases with age. For example, the prevalence of medically unexplained physical symptoms (chronic fatigue, fibromyalgia and multiple chemical sensitivity) in Canadians increases with age from 1.6% of people aged 12 to 24 years, to 6.9% in people 45 to 64 years old.(9) In a Statistics Canada survey of Canadian nurses, 1.4% of nurses younger than 35 years reported chemical sensitivities, which increased to 3.7% in nurses 35-44 years old, and 4.3% and 4.8% in successive decades.(11) Similarly, in studies in Arizona, 15% of college students and 37% of elderly participants reported heightened sensitivities to chemicals.(30,40) Increasing prevalence of sensitivities with age is relevant for the aging workforce, as well as for care of the elderly.

Unlike perfumes and moulds, electromagnetic fields are usually not perceived. Similarly, electromagnetic sensitivities, while plausible,(41) are poorly recognized. The prevalence of electromagnetic sensitivities is estimated to be 1-3% of the population in various countries.(42)


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