"Defining Multiple Chemical Sensitivity" is a carefully documented story, written to establish knowledge and truth based on scienfific method. The first chapters cover some of the latest work in biomarkers for demonstrating chemical poisoning. This poisoning may occasionally be followed by the complex of symptoms called Multiple Chemical Sensitivity Syndrome (MCSS). Biomarkers (medically verifiable tests) include measurable changes in molecules, biochemistry, or cells from human tissue or fluids. Included here are auditory and visual evoked (or "event-related") potentials (ERPs), SPECT scans, acute intermittent porphyrinuria, and changes in levels of cytochrome P-450. These papers go a long way towards providing an understanding of why the chemically poisoned experience such brain fog and react to so many things. There is information on how to prevent/counter attacks. Donald Dudley's chapter, "MCS: Trial by Science" shows how the influence of the olfactory system has been quite underestimated in medical science. 20 MCS patients (under Cullen's definition) were exposed to substances like formaldehyde, MEK, perfume, diesel, a whiff of felt pen... - all chemicals having 6 or fewer carbon fragments in their volatile component. Neurotransmitters from the olfactory system (like glutamate and NMDA), also have molecules with this structure. It is thought that the 6-or-less carbon chemicals act as agonists for the glutamate and other amino acids. And these are the same amino acids which are implicated in brain cell injury - eg stroke, pain, depression and degenerative brain disease. In the study, stimuli were given to eyes and ears - a changing checker board and clicks, before and after the chemical exposures. Electrodes measured how long the brain took to react and how much brain reaction there was. The findings were dramatic. Gunnar Heuser's chapter covers SPECT brain scanning; pictures of the brain which show how the oxygen-carrying blood flow is impaired in the frontal, temporal and parietal lobes in people with exposure to neurotoxic chemicals. This hypoperfusion is further decreased on exposure to, for instance, perfume. Mathematical tasks did not light up the appropriate areas of the brain. He suggests possibilities to explain these findings. These kinds of brain affects were actually detected in a study on DDT in 1966; this research was never followed up. However progress is being made - I liked Eileen McCarty's first chapter parting shot: "A cosmetic salesperson related her poorly adhering nail polish to the lessening of formaldehyde in the formula...". The book has lots of interesting "bits". Porphyrias are deficits of certain enzymes required for the production of heme. Heme is used to produce haemoglobin (for carrying oxygen and carbon dioxide in the blood), and cytochromes (for breaking down such things as steroids, drugs, pollutants, mutagens and natural plant and animal products. Prozac and aldehydes have been shown to inhibit cytochrome P-450. Porphyrias were an extremely rare hereditary condition (remember "The Madness of King George?") usually with a single enzyme missing. But specific testing (through the Mayo Lab) shows how a chemical exposure can cause a multiple enzyme deficit. Bonnye Matthews, in this chapter, gives a clear explanation of the process. She demonstrates that for the first time a model of MCSS is possible. Some Gulf War veterans have also tested positively for toxic-induced porphyrias. The information in this chapter on the substances which can set off an attack is vital. Though there is a great deal of common sense in this book, it's not a light read - there's necessary information for medical professionals - GPs, neurologists, neuropsychologists, psychiatrists, occupational health physicians, allergists, immunologists, cardiologists, gastro-intestinal specialists, anaesthesiologists... in fact it should be compulsory reading at medical schools and for all practising doctors, such are the wide-ranging affects of chemical poisoning. Bonnye unravels the medical detective story that is behind MCS Syndrome - the unethical and incompetent research and papers and medical assessments which were designed to deny compensation by showing MCS as psychosomatic. (The spinoffs are that these papers are now used in countries like New Zealand to deny claims based on MCSS.) But the book's not a witch-hunt - more of a plea for justice and open-mindedness in establishing facts. Bonnye Matthews also tells her own story - because she was (unwittingly at first) in the thick of it as a research subject and recipient of workers' compensation (for a while anyway) in Washington. Her unecessary medical procedures - the methacholine challenge, the venous punctures, even being forced to attend appointments downtown against the advice of her treating physicians are horrifying in their consequences. And loads more including a legal section which shows how a scheme which was intended to be no-fault insurance for work-related individuals has become an adversarial process (and this is Washington, not New Zealand). The measured title of this book belies a gripping read which may make you feel outraged and sick. Please read this book.