New Study Provides a Link between Common Chemicals and ‘Unexplained’ Chronic Illnesses

Could your new home with its fresh paint, carpet, as well as cleaning products and pesticides used around the place, cause illnesses such as fibromyalgia and chronic fatigue syndrome?

A new paper provides a long-awaited link between exposures to common chemicals and so-called unexplained illnesses. It also for the first time asserts a mechanism for the how and why this happens – a two-stage disease process called toxicant-induced loss of tolerance, or TILT.

The paper is co-authored by Claudia S. Miller, MD, professor emeritus, and Raymond F. Palmer, PhD, professor, both in family and community medicine at The University of Texas Health Science Center at San Antonio, also referred to as UT Health San Antonio. They are joined by Dr. Shahir Masri, Program in Public Health, University of California-Irvine; and Dr. Nicholas Ashford, Sociotechnical Systems Research Center, Massachusetts Institute of Technology.

Published in the May 27 edition of the international journal Environmental Sciences Europe, the paper titled, “Toxicant-induced loss of tolerance for chemicals, foods, and drugs: assessing patterns of exposure behind a global phenomenon,” reviews eight events in which groups of individuals shared the same exposure to chemicals and developed multi-system symptoms and new-onset intolerances, either through a single major event or repeated low-level exposures.

Those individuals included employees at U.S. Environmental Protection Agency headquarters after new carpeting was installed; Gulf War veterans; casino workers exposed to pesticides; pilots and flight attendants exposed to fume events; firefighters responding to the World Trade Center tragedy; surgical implant patients; those exposed to mold at home or in the workplace; and tunnel workers exposed to solvents.

Mixed volatile and semi-volatile organic compounds – including some chemicals found in everyday products used to build and maintain homes – were prevalent in those exposures, as were pesticides and combustion products. The exposures suggest the role of TILT, first identified by Dr. Miller from her background as an allergist, immunologist and environmental scientist to explain a new class of environmentally initiated illnesses.

“This paper provides a new link between contemporary environmental exposures and numerous ‘unexplained’ illnesses and syndromes including Gulf War illness, breast implant Illness, chronic fatigue syndrome, fibromyalgia and others, by enumerating TILT,” Dr. Miller said. “TILT represents a new class of environmentally induced diseases that share the same underlying bio-mechanism.”

That underlying mechanism, says Dr. Miller, involves the activation of “mast cells,” which are the “first responders” to xenobiotics or foreign substances like chemicals and viruses.

She notes that the branch of the immune system involving “immunoglobulins,” or proteins that function as antibodies, has been well-studied, but a less well-recognized branch is cellular or cell-mediated immunity. This is the ancient part of the immune system in which mast cells, originating in the bone marrow, migrate to areas located between tissues and the external environment where they then reside.

They can be sensitized by a single high-level exposure of xenobiotics such as chemicals from a pesticide application, or by repeated lower-level exposures, such as breathing volatile organic compounds (VOCs) from remodeling or new construction. Thereafter, even low levels of these and other unrelated chemicals can cause the mast cells to release hundreds of inflammatory chemicals, resulting in allergic-like reactions – some very severe.

Dr. Miller says these disabling conditions have exploded since World War II, coinciding with a massive increase in the production of synthetic chemicals along with their use indoors. This has become even more problematic since the 1970s when energy conservation efforts led to tightly sealed homes, schools and workplaces where fresh air is absent or minimal.

As a result, she says, unprecedented levels of these novel chemicals are released and inhaled from construction materials and furnishings, as well as from substances deliberately released into the air or applied to surfaces. These include cleaning products, fragrances, tobacco smoke, mothballs, disinfectants, and emissions from gas stoves and heaters. Mold in water-damaged buildings can also release toxic chemicals into the air.

The consequences, she says, are more and more chemically exposed and disabled individuals, including and especially children. (An earlier paper by Dr. Miller found that children of chemically intolerant mothers have almost triple the risk of developing ADHD or autism.).

The new paper’s findings are expected to be used by public health scientists, physicians and policymakers seeking to limit harmful exposures and prevent future disease.

“We hope the findings are useful to clinicians, so that they can make a difference for the growing number of people whose lives have been upended by TILT,” said Carlos Roberto Jaén, MD, PhD, FAAFP, chair of family and community medicine at UT Health San Antonio, and a member of the National Academy of Medicine.

“Treatment first requires avoidance or elimination of initiating exposures, and then reducing triggering exposures,” he said. “Carefully selected medications can be helpful. However, many common or formerly tolerated drugs can trigger symptoms in these individuals.”

The paper cites a validated questionnaire developed by Dr. Miller called the QEESI, or Quick Environmental Exposure and Sensitivity Inventory, which has become the international reference standard for research and diagnosis of chemical intolerance. Subsequently, a three-question version called the BREESI, for Brief Environmental Exposure and Sensitivity Inventory, was developed with Dr. Palmer for clinicians to use in identifying chemically intolerant patients and for epidemiologists to screen large populations.

Go to for more information and to download the free BREESI and the QEESI.

Editor’s Note: This news release was first posted at UT Health San Antonio.