L'Association pour la santé environnementale du Québec / Environmental Health Association of Québec


Extract from ‘The Medical Perspective on Environmental Sensitivities’

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

Read the full report

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)


(1) Amdur MO, Doull J, Klaassen CD. Casarett and Doull’s toxicology: the basic science of poisons. 4th ed. 1991.
(2) Lacour M, Zunder T, Schmidtke K, Vaith P, Scheidt C. Multiple chemical sensitivity syndrome (MCS)–suggestions for an extension of the U.S. MCS-case definition. Int J Hyg Environ Health. 2005;208:141-151.
(3) Miller CS. The Compelling Anomaly of Chemical Intolerance. Annals of the New York Academy of Sciences. 2001;933:1-23.
(4) Multiple chemical sensitivity: a 1999 consensus. Arch Environ Health. 1999;54:147-149.
(5) McKeown-Eyssen GE, Baines CJ, Marshall LM, Jazmaji V, Sokoloff ER. Multiple chemical sensitivity: discriminant validity of case definitions. Arch Environ Health. 2001;56:406-412.
(6) Johansson O. Electrohypersensitivity: State-of-the-Art of a Functional Impairment. Electromagn Biol Med. 2006;25:245-258.
(7) Bailey WH. Health effects relevant to the setting of EMF exposure limits. Health Phys. 2002;83:376-386.
(8) Havas M. Electromagnetic hypersensitivity: biological effects of dirty electricity with emphasis on diabetes and multiple sclerosis. Electromagn Biol Med. 2006;25:259-268.
(9) Park J and Knudson S. Medically unexplained physical symptoms. Statistics Canada . 12-1-2007.
(10) Statistics Canada, Health Statistics Division. How healthy are Canadians? Health Reports – Supplement to Volume 16 catalogue no. 820003-XPE. 2006. Canadian Institute for Health Information. Health Reports.
(11) Statistics Canada. Findings from the 2005 National Survey of the Work and Health of Nurses. Statistics Canada . 11-12-2006.
(12) Caress SM, Steinemann AC. A review of a two-phase population study of multiple chemical sensitivities. Environ Health Perspect. 2003;111:1490-1497.
(13) Kreutzer R, Neutra RR, Lashuay N. Prevalence of people reporting sensitivities to chemicals in a population-based survey. Am J Epidemiol. 1999;150:1-12.
(14) Caress SM, Steinemann AC. National prevalence of asthma and chemical hypersensitivity: an examination of potential overlap. J Occup Environ Med. 2005;47:518-522.
(15) Meggs WJ, Dunn KA, Bloch RM, Goodman PE, Davidoff AL. Prevalence and nature of allergy and chemical sensitivity in a general population. Arch Environ Health. 1996;51:275-282.
(16) McKeown-Eyssen G, Baines C, Cole DE et al. Case-control study of genotypes in multiple chemical sensitivity: CYP2D6, NAT1, NAT2, PON1, PON2 and MTHFR. Int J Epidemiol. 2004;33:971-978.
(17) Costa LG, Richter RJ, Li WF, Cole T, Guizzetti M, Furlong CE. Paraoxonase (PON 1) as a biomarker of susceptibility for organophosphate toxicity. Biomarkers. 2003;8:1-12.
(18) Furlong CE, Cole TB, Jarvik GP et al. Role of paraoxonase (PON1) status in pesticide sensitivity: genetic and temporal determinants. Neurotoxicology. 2005;26:651-659.
(19) Cole TB, Jampsa RL, Walter BJ et al. Expression of human paraoxonase (PON1) during development. Pharmacogenetics. 2003;13:357-364.
(20) Haley RW, Billecke S, La Du BN. Association of low PON1 type Q (type A) arylesterase activity with neurologic symptom complexes in Gulf War veterans. Toxicol Appl Pharmacol. 1999;157:227-233.
(21) La Du BN, Billecke S, Hsu C, Haley RW, Broomfield CA. Serum paraoxonase (PON1) isozymes: the quantitative analysis of isozymes affecting individual sensitivity to environmental chemicals. Drug Metab Dispos. 2001;29:566-569.
(22) Schnakenberg E, Fabig KR, Stanulla M et al. A cross-sectional study of self-reported chemical-related sensitivity is associated with gene variants of drug metabolizing enzymes. Environ Health. 2007;6:6.
(23) Baines CJ, McKeown-Eyssen GE, Riley N et al. Case-control study of multiple chemical sensitivity, comparing haematology, biochemistry, vitamins and serum volatile organic compound measures. Occup Med (Lond). 2004;54:408-418.
(24) Miller CS, Gammage RB, Jankovic JT. Exacerbation of chemical sensitivity: a case study. Toxicol Ind Health. 1999;15:398-402.
(25) Brasche S, Bullinger M, Morfeld M, Gebhardt HJ, Bischof W. Why do women suffer from sick building syndrome more often than men?–subjective higher sensitivity versus objective causes. Indoor Air. 2001;11:217-222.
(26) McKeown-Eyssen GE, Sokoloff ER, Jazmaji V, Marshall LM, Baines CJ. Reproducibility of the University of Toronto self-administered questionnaire used to assess environmental sensitivity. Am J Epidemiol. 2000;151:1216-1222.
(27) Joffres MR, Williams T, Sabo B, Fox RA. Environmental sensitivities: prevalence of major symptoms in a referral center: the Nova Scotia Environmental Sensitivities Research Center Study. Environ Health Perspect. 2001;109:161-165.
(28) Gibson PR, Elms AN, Ruding LA. Perceived treatment efficacy for conventional and alternative therapies reported by persons with multiple chemical sensitivity. Environ Health Perspect. 2003;111:1498-1504.
(29) Caress SM, Steinemann AC, Waddick C. Symptomatology and etiology of multiple chemical sensitivities in the southeastern United States. Arch Environ Health. 2002;57:429-436.
(30) Caress SM, Steinemann AC. Prevalence of multiple chemical sensitivities: a population-based study in the southeastern United States. Am J Public Health. 2004;94:746-747.
(31) Shannon M, Woolf A, Goldman R. Children’s environmental health: one year in a pediatric environmental health specialty unit. Ambul Pediatr. 2003;3:53-56.
(32) Woolf A. A 4-year-old girl with manifestations of multiple chemical sensitivities. Environ Health Perspect. 2000;108:1219-1223.
(33) Bornehag CG, Sundell J, Hagerhed-Engman L, Sigsggard T, Janson S, Aberg N. ‘Dampness’ at home and its association with airway, nose, and skin symptoms among 10,851 preschool children in Sweden: a cross-sectional study. Indoor Air. 2005;15:48-55.
(34) Savilahti R, Uitti J, Laippala P, Husman T, Roto P. Respiratory morbidity among children following renovation of a water-damaged school. Arch Environ Health. 2000;55:405-410.
(35) Guillette EA. A broad-based evaluation of pesticide-exposed children. Cent Eur J Public Health. 2000;8 Suppl:58-9.:58-59.
(36) Meklin T, Potus T, Pekkanen J, Hyvarinen A, Hirvonen MR, Nevalainen A. Effects of moisture-damage repairs on microbial exposure and symptoms in schoolchildren. Indoor Air. 2005;15 Suppl 10:40-7.:40-47.
(37) Menzies IC. Disturbed children: the role of food and chemical sensitivities. Nutr Health. 1984;3:39-54.
(38) Grandjean P, Harari R, Barr DB, Debes F. Pesticide exposure and stunting as independent predictors of neurobehavioral deficits in Ecuadorian school children. Pediatrics. 2006;117:e546-e556.
(39) Grandjean P, Landrigan JP. Developmental neurotoxicity of industrial chemicals. The Lancet. 2006;DOI:10.1016/S0140-6736(06)69665-7.
(40) Bell IR, Schwartz GE, Peterson JM, Amend D. Self-reported illness from chemical odors in young adults without clinical syndromes or occupational exposures. Arch Environ Health. 1993;48:6-13.
(41) Huss A, Roosli M. Consultations in primary care for symptoms attributed to electromagnetic fields–a survey among general practitioners. BMC Public Health. 2006;6:267.:267.
(42) Mild KH, Repacholi M, van Deventer E, and Ravanzzani P. Proceedings, International Workshop on EMF Hypersensitivity, Prague, Czech Republic, October 25-27, 2004. 2006.