Multiple Chemical Sensitivity: Recognition and Management. A document on the health effects of everyday chemical exposures and their implications

1. There has been an enormous increase in the production and use of synthetic chemicals and in exposure to pollutants this century, which has accelerated in the last 50 years. Five million different chemicals are now recognized and relatively few of the chemicals in use have been adequately tested for toxicity to man or the environment. Of the 3000 or so in large-scale use, the 'minimal' toxicity data required by the Organization for Economic Co-operation and Development (OECD) for a preliminary assessment of health hazards to humans are not publicly available for 75%. There has been little study of exposure to combinations of different chemicals, either simultaneously or in sequence. 2. Establishing the chronic effects of any exposure is very difficult, even in experimental animals. In humans who are regularly exposed to chemical cocktails that vary from day to day and year to year, it becomes almost impossible unless the outcome is a very rare and well-documented condition. However, it is equally impossible to establish that such exposures are without risk. 3. Long-term ill effects have been reported from chronic exposure to heavy metals and by a minority of individuals after the exposure of defined populations to synthetic or pollutant chemicals-chemical accidents, pesticide exposure, 'sick' buildings, implants, etc. Most of these individuals report that their late symptoms are exacerbated by ambient exposures to volatile organic chemicals (VOCs) emitted by everyday products (for instance, perfumes, washing powders and cigarette smoke), which were previously tolerated without trouble and indeed often enjoyed. Similar chronic conditions occurring in other individuals, after single toxic or sub-toxic exposures, or prolonged low-dose exposure, tend to be overlooked. This condition is referred to as multiple chemical sensitivity (MCS). 4. The genuine nature of MCS has been recognized by officially commissioned reports from independent scientists in the USA and the UK, who have concluded that it is a valid diagnosis and a sometimes disabling condition, although all have stressed the need for further research. 5. Because of their biological roles, it has been suggested that pesticides (designed to interfere with enzymes) and hormone mimics may have a particular place in inducing MCS. However, the evidence also implicates VOCs and other compounds such as diesel particulates and the nitrogen oxides. 6. A large study in Bristol has found associations of air freshener and aerosol use with increased prevalence of certain symptoms in both mothers and babies. 7. Patients with MCS are often treated as if their symptoms are psychologically caused. There is no good evidence for this. On the other hand, double-blind challenges have provided positive evidence for the provocation of symptoms by certain chemicals (varying in different patients) at levels too low to be recognized by the patient; challenge has been reported to cause changes in brain activity on SPECT scans. 8. These patients are usually found, on investigation, to be suffering also from the effects of hidden' allergy (intolerance) to a number of different foods and food additives. The symptom reactions they experience are often dissociated in time from the ingestion of the trigger food in such a way that the connection has not previously been made.