Fungal Fallout: CDC Report Exposes Blastomycosis Risks for Indoor Air Investigators

A 2025 CDC report published in the Morbidity and Mortality Weekly Report details the largest documented U.S. outbreak of blastomycosis — a fungal lung disease — among paper mill workers in Michigan between November 2022 and May 2023. The investigation identified 162 cases out of 645 workers, with illness peaking in March 2023. Despite extensive sampling of soil, dust, and HVAC systems, no environmental source of Blastomyces spores was detected. For indoor air quality (IAQ) consultants, the findings underscore the complexity of detecting biologic contaminants in industrial environments where mechanical ventilation, organic debris, and moisture converge to create potential reservoirs for microbial exposure.

From an exposure-assessment standpoint, the outbreak highlights key diagnostic and control challenges. Though 12% of affected workers required hospitalization and one death occurred, the report stresses that Blastomyces likely infiltrated the mill through unfiltered ventilation systems or open bays rather than proliferating indoors. Figures and tables throughout the report — including Figure 1 (page 2) showing the sharp spike in cases and Figure 2 (page 4) mapping infections by work area — illustrate how airborne pathogens can disperse across departments, from maintenance zones to administrative offices. For consultants conducting IAQ investigations, this case study reinforces the value of integrated epidemiologic surveillance and building-system forensics to pinpoint elusive bioaerosol pathways.

For those engaged in IAQ remediation and consulting, the 2025 CDC findings serve as a call to elevate biological hazard awareness beyond molds and bacteria. The paper mill’s mitigation response — which included upgrading HVAC filtration, cleaning ductwork, and instituting respiratory protection protocols — mirrors best practices familiar to industrial hygienists. Yet the inability to detect the fungus even after 533 environmental samples also illustrates a persistent gap in field diagnostics for fungal spores in complex environments. The report concludes that rigorous ventilation maintenance, moisture control, and worker training remain essential tools in preventing airborne fungal outbreaks in industrial and commercial indoor settings.

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Toxic Vapors Under Scrutiny: Connecticut Study Highlights PERC Risks for Indoor Air Consultants

A 2024 Connecticut Department of Public Health (DPH) health consultation, prepared in cooperation with the Agency for Toxic Substances and Disease Registry, spotlights the persistent indoor air challenges tied to dry-cleaning operations. The investigation centered on tetrachloroethylene (PERC), benzene, and trichloroethylene (TCE) — all volatile organic compounds (VOCs) linked to long-term health effects. While the adjoining dance studio posed no threat to occupants, PERC concentrations in the dry-cleaning space exceeded state and federal comparison values, prompting concerns over vapor intrusion, chemical use, and ventilation adequacy. For air quality consultants, this underscores the importance of source identification and continuous monitoring even in commercial settings with prior remediation history.

The report’s detailed exposure and risk modeling reveals that short-term exposure levels for both workers and the public fall below thresholds for noncancer health impacts. However, the assessment warns that chronic exposure — particularly for dry-cleaner employees over 20 years — could elevate lifetime cancer risks above Connecticut’s 1-in-a-million benchmark. Tables throughout the report quantify elevated PERC levels up to 514 µg/m³ compared to a 5 µg/m³ state guideline (see Table 1, page 19), illustrating how even well-maintained facilities can harbor vapor-phase contamination. Investigators stress the necessity of sub-slab vapor sampling and seasonal variability testing to clarify whether contaminants originate from groundwater vapor intrusion or from the cleaning process itself

For indoor air quality (IAQ) professionals, this consultation serves as a field guide in real-world risk communication and remediation strategy. The DPH recommends increased ventilation, substitution of PERC-based solvents, and retesting after mitigation — a triad of measures that align with best practices in IAQ consulting. The case reinforces the value of comprehensive vapor intrusion assessments and collaborative action between regulators, property owners, and remediation experts. Ultimately, Stratford’s example exemplifies a broader truth in the field: legacy contamination and operational emissions can converge to create invisible indoor hazards that demand both vigilance and cross-disciplinary response

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NIOSH Identifies Widespread Mold and Ventilation Failures Threatening Campus Air Quality

A 2025 NIOSH Health Hazard Evaluation of a Connecticut college uncovered long-standing indoor air quality problems caused by dampness, mold, and poor ventilation across multiple campus buildings. Investigators documented years of high indoor humidity, water damage, and condensation from aging ventilation systems, conditions that contributed to mold proliferation and employee health complaints ranging from respiratory irritation to neurological symptoms.

NIOSH inspections revealed widespread moisture intrusion, lack of vapor barriers in crawl spaces, and inadequate maintenance of HVAC systems, which failed to meet ventilation standards. Air sampling reports from 2011–2022 confirmed elevated indoor levels of fungal spores—including Aspergillus, Cladosporium, and Stachybotrys—often surpassing outdoor concentrations, further substantiating the college community’s concerns over indoor contamination and exposure risk.

The agency’s recommendations emphasized structural and procedural controls to restore healthy indoor environments. These include installing vapor barriers, improving drainage, ensuring HVAC maintenance meets ANSI/ASHRAE Standard 62.1-2022, and maintaining indoor humidity between 30–50%. NIOSH also urged the use of its Dampness and Mold Assessment Tool for continuous monitoring and early detection of moisture problems.

To sustain progress, NIOSH advised the college to enhance transparency and communication through an anonymous reporting system and a dedicated environmental quality team. The report concluded that effective moisture control, ventilation management, and open communication are essential for protecting occupant health and maintaining safe indoor air quality across educational facilities

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