Unmasking the Destructive Force of Toxic Fumes

Higher Sensitivity Rates Found in Women

Jun 09, 2024

woman covering her mouth and nose — ©Photo by Allef Vinicius

Over time, regular exposure to polluted breathing air can lead to health problems. When seeking help, symptoms are often not visible (anymore) and doctors don't have an obvious explanation. Nor do they usually think of ‘poisoning’ and even dismiss the symptoms as "not real" or "psychological" - I don’t know which is worse.

The chemical fumes to which crews are regularly exposed can cause (acquired) chronic illness. Many experts agree that even so-called "low levels" of chemicals can cause symptoms of varying intensity, from mild to debilitating. Toxic substances can affect the central nervous system and brain, the respiratory and gastrointestinal systems, and even the skeletal-muscular system. The eyes and ears can also be affected, causing acute visual impairment and chronic hearing loss. These symptoms are increasingly known in the aviation industry as "aerotoxic syndrome". Aerotoxic Syndrome can be compared to "Multiple Chemical Sensitivity" (MCS) or "Toxicant-induced loss of tolerance" (TILT) as they share similar signs and symptoms and have similar triggers. These chemically induced conditions also appear to have a female predominance.

Women are more likely to be sensitive

A study led by epidemiologist Gail McKeown-Eyssen of the University of Toronto suggests that the condition may indeed have a genetic basis.

The study (published in the International Journal of Epidemiology in October 2004) examined genetic differences between women who reported multiple chemical sensitivities and those who did not. The researchers recruited 203 cases and 162 controls from female respondents. They identified multiple chemical sensitivity cases using criteria derived from previous studies, including one by James R. Nethercott. Nethercott defines cases as those with chronic symptoms associated with low-level exposure to chemical agents, and resolve with the removal of exposure.

Women with higher levels of cytochrome P450 2D6, an enzyme encoded by the CYP2D6 gene, are three times more likely to be chemically intolerant than those with the inactive form of the gene. These enzymes work primarily in the liver to detoxify a wide range of chemicals, including caffeine and prescription drugs.

It is also highly expressed in areas of the central nervous system, including the 'substantia nigra', a structure in the mid-brain.

There is considerable variation between individuals in the efficiency and amount of this particular enzyme produced. Therefore, chemicals metabolized by CYP2D6 are metabolized rapidly in some people and slowly in others.

Slow metabolizers are three times more likely to have chemical intolerance than fast metabolizers. Similarly, women with the so-called fast acetylated form of NAT2, the gene that codes for an enzyme that activates both drugs and carcinogens, were four times more likely to report chemical intolerance.

Because the metabolism of some chemicals can produce toxic byproducts (metabolites), people with fast metabolisms could accumulate toxic compounds in their bodies more quickly. "It depends on the compound, what the metabolites are, and how quickly they're cleared from the body, whether having a fast metabolism results in more exposure or less exposure," says McKeown-Eyssen.

People who suffer from chemical intolerance report a wide range of symptoms, including headaches, short-term memory problems, confusion, fatigue, depression, irritability, and breathing difficulties. All of these symptoms and more are reported by affected flight crews and, increasingly, by (frequent) flyers who have been exposed to an (acute) fume event.

It is important to understand that an 'acute' fume event can trigger symptoms that have been dormant for a long time. This means the body's toxic load has been building up until it can take no more. Aircraft crews in particular would be prone to such "out of the blue" moderate to severe reactions. They often express surprise because they were unaware that their bodies had been absorbing and storing small doses of toxic substances over a long time. They may have previously dismissed minor symptoms. What happens now is TILT = the loss of tolerance to toxins - even to minute amounts.

The team around Shahir Masri at the Public Health Department, University of California, published a paper in May 2021, stating that:

“Mixed volatile and semi-volatile organic compounds (VOCs and SVOCs), followed by pesticides and combustion products were most prevalent across TILT initiation events. As a broader category, synthetic organic chemicals and their combustion products were the primary exposures associated with chemical intolerance. Such chemicals included pesticides, peroxides, nerve agents, anti-nerve agent drugs, lubricants and additives, xylene, benzene, and acetone.” (sic - / bold by BB)

Back to the Toronto researchers around Gail McKeown-Eyssen who found that individuals are likely to have certain conditions in several different forms, in one or both of the two genes with the codes: CYP2D6 and NAT2. The latter two codes for enzymes that metabolize pharmaceutical chemicals that target the central nervous system, including antidepressants, neurotoxic substances that become carcinogenic when metabolized, and even the body's neurotransmitters. NAT2 also plays a role in metabolizing several drugs and toxic chemicals, including aromatic amines - a "simple aromatic amine" is benzene.

The researchers found an even stronger association in women with the fast metabolizing form of both CYP2D6 and NAT2. These women were 18 times more likely to suffer from multiple chemical sensitivities than controls, research is ongoing.

Andreas Kortenkamp and his team state in their paper Low-Level Exposure to Multiple Chemicals: Reason for Human Health Concerns?: “The widely held view that mixtures of dissimilarly acting chemicals are “safe” at levels below NOAELs is not supported by empirical evidence. We show that this view is also based on the erroneous assumption that NOAELs can be equated with zero-effect levels. Thus, on the basis of published evidence, it is difficult to rule out the possibility of mixture effects from low-dose multiple exposures.” (sic)

Long-term and permanent debilitating health problems as a result of chronic exposure to neurotoxic, fertility, and DNA-damaging carcinogenic chemicals are increasing. Aerotoxic Syndrome, an occupational hazard of aviation, can lead to chronic chemical sensitivity, among other debilitating immune disorders, and is experienced by countless flight crew members.

Aerotoxic Syndrome is legitimate and deserves to be properly recognized by doctors, the aviation industry, and, most importantly, employers' liability insurers.

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Share Take-Off: Aviation's Wounded Canaries

Unmasking the Destructive Force of Toxic Fumes

Higher Sensitivity Rates Found in Women

The unregulated flow of unfiltered and recycled toxic fumes coming from a mix of pyrolyzed jet fuel and engine oils into the cabin-breathing air is causing many flight safety and health issues for cabin crew, pilots, and passengers. Aerotoxic Syndrome.

Women are more likely to be sensitive

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