25.8Figure 2, (6)
Low-Level Exposure and Chronic Symptoms
Questions regarding the impact of repeated low-level exposures to potentially toxic agents exist within the circumstances of both GWI and SBS. For GWI, "evidence of chronic and delayed consequences to physiological systems from repeated low-level AChEi exposure" was found, with it being added that "evidence for persistent and delayed effects of low-level exposure is accruing".(1)
Paralleling the chronic nature of GWI, in 2004 it was observed that "there is mounting evidence that some SBS symptoms do not abate quickly if at all".(7) These researchers then immediately proceeded to note that "evidence by numerous investigations has shown the association of various species of fungi including Penicillium sp and Aspergillus sp and their spores with indoor air-quality problems and SBS",(7) emphasizing the role these two fungi play.
Completing the evidence in this area were findings published Summer 2008 in what is believed to be the first-ever "follow-up study of patients previously referred to hospital" with "non-specific building-related symptoms", SBS.(8) The study followed the experience of approximately 200 such patients who had indeed received hospital clinic treatment, observing that:
"The level and severity of symptoms decreased over time, although nearly half of the patients claimed that symptoms were more or less unchanged after 7 years or more, despite actions taken. Twenty-five percent of the patients were on the sick-list, and 20% drew disability pension due to persistent symptoms at follow-up."(8)
The study also found that only about 7% of those patients followed had fully recovered from SBS's effects.(8)
Evidence would seem to exist that repeated low-level exposures, in cases of both GWI and SBS, do appear to yield chronic and delayed consequences to physiological systems. It is unfortunate though that the phrase 'low-level' can be somewhat misleading.
500-Fold Larger Exposures and Aerosolized Fungal Fragments
Examining the question of AChEi exposure via the inhalation of aerosolized fungal agents, 2002 research demonstrated that Aspergillus versicolor and Pencillium melinii fungal fragments were found to be "aerosolized simultaneously with spores from contaminated agar and ceiling tile surfaces."(9) The study emphasized that the "considerable immunological reactivity, the high number, and the small particle size of the fungal fragments may contribute to human-health effects that have been detected in buildings with mold problems but had no scientific explanation until now."(9)
Mold fragments, not simply the spores, are thus suggested as harboring the potential to provide a key AChEi-delivery mechanism. Subsequent research further highlighted an extremely significant role for fungal fragments, one as the primary medium for mycotoxin exposure from indoor molds.(10) Specifically, a 2007 Swedish research study found, "indoor molds may fragment into very small airborne mycotoxin-containing particles resulting in up to a 500-fold larger exposure than assumed previously."(10)
Coupling the 2007 study's findings with those from the independent 2002 research, a possible delivery mechanism for mycotoxins -- and potentially AChEis -- at levels hundreds of times higher than previously realized, would indeed seem suggested.
"Why are some ill and not others?"
Exploring beyond the possible role of AChEis in mold-related SBS, beyond the question as to how AChEi exposure might occur, the question of individual sensitivity to an AChEi exposure is raised. Given that we are addressing an onset of symptoms resulting from extended 'low-level' exposures, a question regarding the effects of individual differences in AChEi-detoxification levels exists. We feel that the efforts of several studies are significant to cite in regards to this, with their findings of genetic variants noteworthy.
Returning to the findings published in the Spring 2008 Proceedings of the National Academy of Sciences of the United States of America, of particular significance is the determination that GWV illness was "linked to lower activity of AChEi-detoxifying enzymes and genotypes conferring less-avid AChEi detoxification."(1) The study noted that "low PON activity levels and concentration are significantly associated with multisymptom health problems in GWV", singling out low PON1 activity for emphasis.(1)
Supporting such genetic linkage, a 1999 study's title suffices: "Association of Low PON1 Type Q (Type A) Arylesterase Activity with Neurologic Symptom Complexes in Gulf War Veterans".(11) An independent 2004 study also noted that their "finding parallels others' observation of a link between PON1 heterozygosity" and symptoms in GWV.(12)
Paraoxonase (PON) is an enzyme which is HDL-associated, and "one of many circulating antioxidants thought to play a vital protective role".(13) "The level of PON-1 gene expression is a major determinant of paraoxonase-1 status", according to a 2003 French study.(14)
Evidence of a genetically based susceptibility to AChEi exposure appears to exist. Of course, the key question raised by this hypothesis is the impact mycotoxin-derived AChEi exposures may have, particularly upon those most susceptible, and whether we have come to often term such impact SBS.
AChEi exposure, via inhaled AChEi-rich mycotoxins carried by aerosolized fungal agents, may be a primary but unrealized cause of SBS. Genetic variance, specifically involving low PON activity levels and concentrations, may be a key determinant of susceptibility to SBS. Research is needed to determine the answers to both these questions, as well as potentially that of how broadly, and in what configurations and potencies, AChEis may exist within the range of those fungi typically associated with SBS problems - Penicillium sp, Aspergillus sp, and Stachybotrys sp.