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