HYPERSENSITIVITY to low levels of common chemicals is a ubiquitous public health problem
(1); however, the prevalence of chemical hypersensitivity in the U.S. population has not been previously established. Chemical hypersensitivity--often called multiple chemical sensitivity (MCS)
(2)--is also referred to as toxicant-induced loss of tolerance
(3) or environmental illness.
(4) It is typically acknowledged to be a condition characterized by acute reactions that occur after exposure to even low levels of common chemical products such as fragrances, household cleaners, fresh paints, newsprint, pesticides, and other products that contain petrochemicals.
(5) MCS can produce a wide range of symptoms, and individuals with the hypersensitivity can encounter great difficulty functioning in normal working and living environments.
(6) Although a limited number of epidemiological studies have investigated the regional prevalence of chemical hypersensitivity in the U.S., its national prevalence is speculative. The National Academy of Sciences estimated that up to 15% of the U.S. population experiences some degree of hypersensitivity to common chemicals.
(7) The California Department of Health Services found a 15.9% prevalence of chemical hypersensitivity among Californians,
(8) whereas similar studies in the Atlanta, Georgia, metropolitan area and in New Mexico found prevalences of 12.6%
(9) and 16%,
(10) respectively. These 3 studies used accepted epidemiological methodologies with randomly derived samples. Other published prevalence studies that have used methodologies such as anecdotal evidence, nonrandomly or self-selected subjects, or a broader definition of chemical hypersensitivity have produced varying findings. For instance, a study that relied exclusively on conversations with medical personnel in clinical settings estimated that 2% to 10% of the population experiences hypersensitivity.
(11) Two subsequent studies in Arizona that used self-selected subjects--young adult college students and elderly persons--determined that approximately 15% of the younger group
(12) and more than 37% of the elderly group
(13) reported a hypersensitivity to chemicals. A population survey in rural North Carolina, using a broader definition of MCS that did not distinguish between