Industrial hygienists (IHs) are called upon to investigate exposures to mold in indoor environments, both residential and commercial. Because exposure standards for molds or mycotoxins do not exist, it is important for the industrial hygienist to have a broad knowledge of the potential for exposure and health effects associated with mold in the indoor environment. This review focuses on the toxic effects of molds associated with the production of mycotoxins, and the putative association between health effects due to mycotoxin exposure in the indoor environment. This article contains background information on molds and mycotoxins, and a brief summary and review of animal exposure studies, case reports, and epidemiological studies from the primary literature concerning inhalation of mycotoxins or potentially toxin-producing molds. The relevance of the findings in the reviewed articles to exposures to mold in indoor, non-agricultural environments is discussed. Although evidence was found of a relationship between high levels of inhalation exposure or direct contact to mycotoxin-containing molds or mycotoxins, and demonstrable effects in animals and health effects in humans, the current literature does not provide compelling evidence that exposure at levels expected in most mold-contaminated indoor environments is likely to result in measurable health effects. Even though there is general agreement that active mold growth in indoor environments is unsanitary and must be corrected, the point at which mold contamination becomes a threat to health is unknown. Research and systematic field investigation are needed to provide an understanding of the health implications of mycotoxin exposures in indoor environments.

Experiments were conducted to study the acute inhalation toxicity of T-2 mycotoxin in both young adult and mature mice. For a 10-min aerosol exposure, the 24-hr LC50 of T-2 mycotoxin in young adult mice was 0.08 +/-0.04 mg T-2/liter air and that for mature mice was 0.325 +/-0.1 mg T-2/liter air. Deaths among mice exposed to the higher aerosol concentrations used in this study (i.e., 1.5 to 2.4 mg T-2/liter air) occurred in less than 5 hr. General clinical symptoms in these animals immediately postexposure were tremors, lethargy, stilted gait, and, in some animals, prostration. In experiments separate from the concentration-response studies, total deposition of T-2 aerosol and selective retention of T-2 in the respiratory tract and nasal turbinates were determined analytically from 3H-labeled T-2. When total deposition of T-2 was quantitated, there was excellent agreement between that amount of T-2 deposited and that amount of T-2 predicted from calculations based on aerosol size and animal minute volume. Based on the aerosol deposition data, the LD50 values of T-2 mycotoxins was 0.24 mg/kg for young adult mice and 0.94 mg/kg for mature mice. For mice, inhalation of T-2 mycotoxin is at least 10 times more toxic than systemic administration (LD50 approximately 4.5 mg/kg) and at least 20 times more toxic than dermal administration (LD50 greater than 10 mg/kg).

Predictive modeling is an available tool to assess worker exposures to a variety of chemicals in different industries and product-use scenarios. The European Chemical Agency (ECHA)'s guidelines for manufacturers to fulfill the European Union's legal requirements pursuant to the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) initiative include recommendations for the use of modeling to predict worker exposures. ECHA recommends different models for different target populations (i.e. workers, consumers, environment) and routes of exposure (i.e. skin absorption, ingestion, inhalation), and presents them hierarchically, with Tier 1 models presented as the most simplistic, conservative models and Tier 2 models recommended for further intensive evaluation of substances or preparations. In order to assess these models for one exposure (product-use) scenario, a simulation of the scenario was completed in a controlled environment and the measured results were compared with the modeling outputs. The authors predicted, based on the design of the modeling tools, that all models would overestimate worker exposures under the simulated product-use scenario, with the lower-tiered model producing the most conservative estimate of exposure. In this study, a Tier 1 model and a Tier 2 model were evaluated for comparison with the near-field, far-field (NF-FF) deterministic model and measured experimental results in a real-time worker inhalation exposure assessment. Modeling was conducted prior to actual air monitoring. The exposure scenario that was evaluated involved the application of a toluene-containing spray paint to a work surface. Air samples were collected to evaluate short-term (15-min) and long-term (240-min) exposures. Eight-hour time-weighted averages (8-h TWAs) were calculated and compared with the modeling outputs from the recommended REACH modeling tools and the NF-FF model. A comparison of each of the modeling tools with measured experimental results was generated. The Tier 1 Targeted Risk Assessment tool overestimated the 8-h TWA airborne concentration of toluene in the spray scenario by a factor of 3.61. The higher tiered Advanced REACH Tool and NF-FF models showed greater concordance with experimental results, overestimating the TWA exposure by a factor of 2.92 and 1.96, respectively. In conclusion, the Tier 1 and 2 exposure modeling tools performed as expected for the simulated exposure scenario, providing relatively accurate, though conservative, estimates according to the level of detail and precision accounted for in each model.

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While the critical task of evaluating the hazards of nanomaterials continues, exposure assessments can provide additional information to safeguard workers. The frequent exposure of construction workers to inhalation hazards underscores a pressing need to characterize and quantify nanomaterials in aerosols generated during construction activities. Research was conducted in partnership with affected building trades unions and in collaboration with NIOSH toxicologists to obtain occupationally relevant exposure data. Initial studies took place in a test chamber, in which a skilled tradesperson sprayed or sanded paints and coatings containing ZnO, TiO2, or Ag nanoparticles. The current study, conducted outdoors, investigated exposure to graphene nanoplatelets during cutting, grinding, and tuckpointing of cementitious composites. Personal breathing zone samples were analyzed for elemental carbon (EC) respirable mass concentration and by transmission electron microscopy (TEM) with energy-dispersive x-ray spectroscopy. Wet methods and local exhaust ventilation effectively reduced exposure to graphene; respirable EC was non-detectable when using exposure controls versus up to 3 mg m-3 without. A high proportion of graphene particles observed by TEM were free and not bound to the cement matrix. Compared to the unincorporated graphene, the dimensions of graphene particles observed in air samples were smaller, suggesting a potential physical transformation prior to release from the matrix. Given the dustiness of construction environments, analysis of filter loading prior to collection of TEM samples proved methodologically valuable. These results provide actionable information about exposure risks and controls and support further investigation of the extent to which graphene may alter the toxicity of cement dust.