Stachybotrys chartarum (or S. atra or S. alternans) [CAS No. 67892-26-6] Review of Toxicological Literature

Stachybotrys chartarum is a greenish-black mold in the fungal division Deuteromycota, a catch-all group for fungi for which a sexually reproducing stage is unknown. It produces asexual spores (conidia). The morphology and color of conidia and other structures examined microscopically help distinguish the species from other molds found in indoor air that may contaminate materials in buildings that have suffered water intrusion. S. chartarum may ultimately overgrow other molds that have also produced colonies on wet cellulosic materials such as drywall (gypsum board, wallboard, sheet rock, etc.). Because of the likelihood that it may produce toxic macrocyclic trichothecenes and hemolytic stachylysin (exposure to which may be associated with idiopathic pulmonary hemorrhage [IPH] in infants), S. chartarum exposure is of concern to the members of the general public whose homes and workplaces have been contaminated after water intrusion, to agricultural and textile workers who handle contaminated plant material, and to workers involved in remediation of mold-damaged structures. Dry conidia, hyphae, and other fragments can be mechanically aerosolized as inhalable particulates. Recent work on characterizing the numerous strains or isolates that have been recovered throughout the world has important applications on sampling and analysis for species identification in mold-contaminated buildings and on resolving apparent discrepancies in the environmental and toxicological literature. New assays based on polymerase chain reaction (PCR), immunoassays, and protein translation inhibition assays have improved the accuracy and speed in which S. chartarum can be identified and quantified. In addition, PCR-based methods and other genomic work are elucidating the differences among S. chartarum strains. Strains can be grouped into two chemotypes (basically those that produce macrocyclic trichothecenes and those that do not), and some strains have now been reassigned to a different species, Stachybotrys chlorohalonata. In addition, prior studies of exposure and environmental occurrence may need to be reevaluated with respect to their sampling and laboratory culturing methods. Because S. chartarum is slow growing, use of a nutrient-rich medium favors the growth of other mold species that are invariably present, consequently the actual concentrations of S. chartarum conidia may be seriously underreported. Recent epidemiologic investigations have suggested an association between exposure to S. chartarum and toxic inflammatory effects in infants, in courthouse workers, and in office workers, as well as between S. chartarum and extreme chronic fatigue syndrome in hospital workers. The Centers for Disease Control and Prevention concluded that evidence from current studies does not support a relation between acute PH or hemosiderosis and exposure to S. chartarum. Sick building syndrome and the intensification of asthma have also been linked with elevated indoor levels of Stachybotrys; however, there is not sufficient evidence to substantiate this association. It is generally accepted that building-related asthma and an increased incidence of upper respiratory disease are associated with living or working in a moldy environment; these associations, however, are with molds that comprise many species. S. chartarum was reported to induce sensory irritation, inflammatory, and/or pulmonary responses in mice and rats exposed via intranasal instillation, intratracheal instillation, and inhalation. In one reproductive toxicity study, Stachybotrys caused a decrease in the percentage of pregnant mice. Additionally, statistically significant differences were seen in the frequency of dead, resorbed, and/or stunted fetuses and in the average litter size of live fetuses in treated animals compared to controls. Cytotoxic effects in vitro included induction of tumor necrosis factor-α and interleukin-6 production. Changes in total protein, albumin, pro-inflammatory cytokine, and lactate dehydrogenase in bronchoalveolar lavage fluid were observed in mice exposed to S. chartarum.