Toxic Exposure Induced
Multiple Chemical Sensitivity (MCS) Review,
B. Windham (Ed) {with emphasis on pesticide exposures}
Doctors are increasingly
seeing a unique pattern of illness involving chemically exposed groups in more
than a dozen countries, who subsequently report multisystem symptoms and
new-onset chemical, food, and drug intolerances at levels of exposure below that
affecting most other individuals [1-4]. The common pattern of development of
these intolerances is a compelling anomaly pointing to a new theory of disease,
one that has been referred to as "Toxicant-Induced Loss of Tolerance"
("TILT") or Multiple Chemical Intolerance(CI).
TILT or CI has the potential to explain certain cases of asthma, migraine
headaches, chronic fatigue,
fibromyalgia, as well as other chronic conditions including depression, alzheimer’s disease[12],
and "Gulf War syndrome". It appears to evolve in two stages: (1)
initiation, characterized by a profound breakdown in prior, natural tolerance
resulting from either acute or chronic exposure to chemicals (pesticides,
solvents, toxic metals[4], indoor air contaminants, etc.), followed by (2)
triggering of symptoms by small quantities of previously tolerated chemicals
(traffic exhaust, fragrances, gasoline), foods, drugs, and food/drug
combinations (alcohol, caffeine). Multiple mechanisms of chemical injury that
magnify response to exposures in chemically sensitive patients can include neurogenic inflammation
(respiratory, gastrointestinal, genitourinary), kindling and time-dependent
sensitization (neurologic), impaired porphyrin metabolism (multiple
organs), and immune activation. Severe CI is a characteristic of 20-47% of
individuals with CFSand/or fibromyalgia,
all patients with multiple chemical sensitivity (MCS), and approximately 4-6%
of the general population. In the general population, 15-30% report at least
minor problems with CI[2]. The levels of chemicals
reported to trigger CI would normally be considered nontoxic or subtoxic.
However, host factors--e.g., individual differences in susceptibility to neurohormonal sensitization
(amplification) of endogenous responses--may contribute to generating a disabling
intensity to the resultant multisystem dysfunctions in CI. One site for this
amplification may be the limbic system of the brain, which receives input from
the olfactory pathways and sends efferents to
the hypothalamus and the mesolimbic dopaminergic [reward]
pathway. Chemical, biologic, and psychological stimuli can initiate and elicit
sensitization. In turn, subsequent activation of the sensitized limbic and mesolimbic pathways
can then facilitate dysregulation of behavioral, autonomic,
endocrine, and immune system functions. Research to date has demonstrated the
initiation of neurobehavioral sensitization by volatile organic compounds,
toxic metals, and pesticides, as well as sensitizability of
cardiovascular parameters, beta-endorphin levels, resting EEG alpha-wave
activity, and divided-attention task performance in persons with CI. Chronic pesticide exposure has been found to be a common
cause of MCS and related symptoms such as CFS, Fibromyalgia, Migraine
Headaches, Depression,[1-3,5-11] etc. as well as Alzheimer’s
Disease[12].
Synergistic effects
and susceptibility factors have
significant effects on who is affected by toxic exposures and to what eztent.
References:
(1) The compelling
anomaly of chemical intolerance, Miller
CS, Ann N Y Acad Sci.
2001 Mar;933:1-23; & Elevated nitric oxide/peroxynitrite mechanism
for the common etiology of multiple chemical sensitivity, chronic fatigue
syndrome, and posttraumatic stress disorder. Pall ML, Satterlee JD . Ann N Y Acad Sci.
2001 Mar; 933:323-9.
(2) Illness from low
levels of environmental chemicals: relevance to chronic fatigue syndrome and
fibromyalgia. Bell IR, Baldwin CM, Schwartz GE. Am
J Med. 1998 Sep 28;105(3A):74S-82S; &
Chronic fatigue syndrome following a toxic exposure; Racciatti D, VecchietJ, Ceccomancini A, Ricci
F, Pizzigallo E. Sci Total Environ.
2001 Apr 10;270(1-3):27-31.
(3)Profile of patients
with chemical injury and sensitivity; Ziem G, McTamney J. Environ
Health Perspect. 1997 Mar;105 Suppl 2:417-36.
(4 )Mechanisms
of mercury induced chemical sensitivity, chronic fatigue, fibromyalgia; B
Windham (Ed.), www.flcv.com/cfsfm.html
(5) [Chronic
fatigue syndrome and multiple chemical hypersensitivity after insecticide
exposure] Fernández-Solŕ J, Munné Mas P et al;Med Clin (Barc). 2005 Apr 2;124(12):451-3.
(6) The specificity of
the CDC-1994 criteria for chronic fatigue syndrome: comparison of health status
in three groups of patients who fulfill the criteria; Kennedy G, Abbot NC,
Spence V, Underwood C, Belch JJ. Ann Epidemiol. 2004 Feb;14(2):95-100.
(7) Peripheral
cholinergic function in humans with chronic fatigue syndrome, Gulf War syndrome
and with illness following organophosphate exposure; Khan F, Kennedy G, Spence
VA, Newton DJ, Belch JJ. Clin Sci (Lond). 2004 Feb;106(2):183-9.
(8) Association between
human paraoxonase gene polymorphism and
chronic symptoms in pesticide-exposed workers; Lee BW, London L, Paulauskis J, Myers J, Christiani
DC. J Occup Environ Med. 2003 Feb;45(2):118-22.
(9) A genetic rat model
of cholinergic hypersensitivity: implications for chemical intolerance, chronic
fatigue, and asthma; Overstreet DH, Djuric V. Ann
N Y Acad Sci. 2001 Mar;933:92-102.
(10) Locomotor and sensorimotor performance
deficit in rats following exposure to pyridostigmine bromide, DEET,
and permethrin, alone and in combination. Abou-Donia MB,
Goldstein LB, Jones KH, Khan WA. Toxicol Sci. 2001 Apr;60(2):305-14; & (b) Pesticide
neurotoxicity in Europe: real risks and perceived risks. Ray
DE. Neurotoxicology. 2000 Feb-Apr;21(1-2):219-21.
(11)
Endocrine Disruption and Perspective Human Health Implications: A Review, S. Poongothai, R. Ravikrishnan, Department
of Toxicology, International Institute of Biotechnology and Toxicology, The
Internet Journal of Toxicology™ ISSN: 1559- & Endocrine Disruption and
Perspective Human Health Implications , JPHE, Jan 2017, http://jphe.amegroups.com/article/view/3669/4423 & https://www.niehs.nih.gov/health/topics/agents/endocrine/index.cfm
(12) Repeated Exposure to Pesticides
Increases Risk of Alzheimer’s Disease, K.M. Hayden, Neurology, 2010;
74:1524-1530; & The Mercury/Toxic Metal Connection to Alzheimer’s
Disease, Review, B. Windham (Ed.), http://www.myflcv.com/alz.html
