Multiple Chemical Sensitivity: Who is chemically sensitive? Part 3 of 7
Because MCS is difficult to diagnose, it’s challenging to know exactly who and what percentage of the population develop debilitating symptoms. A broad view of someone who has been diagnosed would be a someone over 35 years old. 1 More specifically, it would be a 40-year-old female who experienced symptoms before she was 30. However, there are a large percentage of Persian Gulf War veterans who have reported MCS symptoms since they returned in the early 1990’s. 2
Based on Caress and Steinemann’s 2004 study, MCS affects approximately 13% of the population. 3 They state that this number is similar to a study done in California that found 15% of the population experienced chemical sensitivities. Only 3.1% of these had been diagnosed by a medical doctor. Of this group, 30% had asthma and 45% had received medical treatment. A more recent study by Claudia Miller (2013) found that 6% of people visiting a primary care clinic were “greatly affected by chemical pollutants in their environment” and “another 15.8% were moderately affected. ”4 Miller proposes a genetic component. “Asthma, depression and panic disorder run in families of sufferers.” 5 In her view, MCS or what she refers to as TILT (toxicant-induced loss of tolerance), “emerges from a more sensitive, highly excitable limbic system.” 6 It’s helpful for understanding what’s going on in one’s body and brain to know how the limbic system works.
The limbic system includes the olfactory bulbs, hippocampus, amygdala, anterior thalamic nuclei, fornix columns of fornix, mammillary body, septum pellucidum, habenular commissure, cingulate gyrus, parahippocampal gyrus, limbic cortex, and limbic midbrain areas 7 (whew!). Your olfactory bulbs are your sense of smell. The hippocampi consolidate information from short-term memory to long-term memory and are involved in spatial navigation. Memory loss and disorientation are the first symptoms of Alzheimer’s disease and indicate damage to the hippocampus. 8 The amygdalae perform memory processing, decision-making, and emotional reactions. This area of the brain is connected to the formation and storage of memories associated with emotional events, such as fear condition.9 The anterior nuclei are involved in the modulation of alertness, learning, and episodic memory, and spatial navigation relative to head movement. 10 The fornix is associated with memory loss such as recall11 (neuroanatomy). The mammillary bodies are responsible for spatial memory and recollective memory— times, places, associated emotions, and the who, what, when, where and why knowledge of past personal experiences. 12 The cingulate cortex is an integral part of emotion formation and processing, learning, and memory. It links behavioral outcomes to motivation and plays a role in executive function and respiratory control. Your executive functions include working memory, reasoning, task flexibility, and problem solving, planning and execution. 13 It controls and manages other cognitive processes. 14 The parahippocampal gyrus plays an important role in memory encoding and retrieval. 15 The entorhinal cortex functions as a hub in a network for memory and navigation. It is involved in declarative memories and spatial memories, including memory formation, memory consolidation, and memory optimization in sleep. This is the first area of the brain to be affect by Alzheimer’s disease. 16 The midbrain is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, alertness and temperature regulation. 17
This is a lot of information to consolidate and try to remember. The most important thing to understand is that exposure to chemicals can be experienced through smell (olfactory bulbs) and result in problems with memory formation, processing, and recall; alertness; learning; spatial navigation, including disorientation and vertigo; emotions, including motivation; and your central nervous system— vision, hearing, motor control, sleeping, waking, alertness, and temperature regulation. Chemical exposure affects your brain— aka your ability to think and since your brain controls your body, it affects how well your body works, too.