Health and Wellness, Injuries and Illness

Understanding Workplace Fungal Threats

A Michigan paper mill recently had to close for intensive cleaning following an outbreak of workplace fungal infections. There were 21 confirmed cases, including 1 fatality, and 76 people at the mill were classified as having probable cases of blastomycosis.

Fungal diseases like blastomycosis, coccidioidomycosis (Valley Fever), and histoplasmosis can infect anyone, according to the Centers for Disease Control and Prevention (CDC), regardless of immune status.

In the CDC’s most recent surveillance report for 2019, it reported 240 cases of blastomycosis in 5 states: Arkansas, Louisiana, Michigan, Minnesota, and Wisconsin. Minnesota and Wisconsin accounted for 75 percent of all cases (179). The CDC received reports of 1,124 cases of histoplasmosis and 20,061 cases of coccidioidomycosis that year.

Fungal infections usually are acquired by inhaling fungal spores and can progress to life-threatening diseases of the lungs or other organs, according to the CDC.

At the Michigan paper mill, the National Institute for Occupational Safety and Health (NIOSH) performed a health hazard evaluation and offered recommendations for the employer, including encouraging it to inspect all heating, ventilation, and air-conditioning (HVAC) systems and contract with a licensed ventilation engineer or building scientist to inspect the ductwork for evidence of water incursion and microbial growth.

NIOSH also recommended that the employer supply its employees with N95 filtering facepiece respirators for voluntary use to minimize exposure to Blastomyces, the fungus that causes blastomycosis.

In addition, the institute cautioned the employer to carefully consider any activities beyond regular mill operations with the potential to disturb dirt, soil, or organic material on the mill property that may be contaminated with Blastomyces.


Histoplasmosis is an infection caused by the Histoplasma fungus, which lives in the environment, particularly in soil that contains large amounts of bird or bat droppings, according to NIOSH. Histoplasma mainly lives in the central and eastern United States, particularly in areas around the Ohio and Mississippi River valleys.

People can get histoplasmosis by breathing in microscopic fungal spores, known as conidia, from the air.

While many people who get histoplasmosis get better on their own without medication, some may experience infections that can become severe and spread from the lungs (dissemination) to other parts of the body, such as the eyes and lymph nodes. Severe or disseminated infections may be common in people with weakened immune systems or other medical conditions.

NIOSH recommends following the industrial hygiene “hierarchy of controls,” beginning with elimination and engineering controls, to prevent Histoplasma exposures in the workplace.

Elimination and engineering controls may include:

  • Excluding bats and birds from buildings;
  • Controlling dust generated when removing bat or bird droppings;
  • Disinfecting potentially contaminated material, such as soil or accumulations of droppings;
  • Properly disposing of material potentially contaminated with Histoplasma; and
  • Controlling aerosolized dust during construction, excavation, and demolition.

Administrative controls include hazard communication, posting health risk warnings, and training. Personal protective equipment (PPE) could include filtering facepiece respirators like N95s, full-facepiece or half-facepiece elastomeric respirators, or powered air-purifying respirators (PAPRs).

Additional PPE for workers removing large amounts of droppings would include coveralls with a hood, gloves, goggles or other eye protection, and disposable shoe coverings.

NIOSH recommends that workers who think they’ve been exposed to Histoplasmaat work contact a crew leader or supervisor and their employer’s occupational health or risk management department. They also should inform their healthcare provider that they work in an area where Histoplasma is common and ask to be tested for histoplasmosis.

Occupations in which Histoplasma exposure is common are bridge workers, construction or demolition workers, farmers or farm laborers, landscapers or tree removal workers, and microbiology laboratory workers.

To reduce instances of histoplasmosis among workers in clinical and research laboratories, NIOSH stresses the importance of containing microbial exposures through aseptic microbiological practices that address the cultivation, storage, and disposal of biohazardous materials; medical surveillance; and staff training and workers’ knowledge of the facility’s laboratory safety manual.

Work activities associated with histoplasmosis risks include construction, demolition, or renovation; disturbing large accumulations of bird or bat droppings (cleaning a chicken coop, scraping droppings from a bridge, or shoveling droppings from a building or other structures) or disrupting plant matter; handling trees or landscaping; soil disruption during digging or excavation; and working in caves.

NIOSH summarized its employer guidance in a December 2021 fact sheet. Employers doing work like construction, demolition, or excavation in areas where Histoplasma is common should develop a site safety plan, according to NIOSH.

Coccidioidomycosis—Valley Fever

While there may be hundreds of cases a year of blastomycosis and over a thousand histoplasmosis cases a year, coccidioidomycosis is a far bigger threat, with tens of thousands of cases a year.

The fungal infection sometimes is referred to as Valley Fever, California fever, desert rheumatism, and San Joaquin fever.

Like blastomycosis and histoplasmosis, coccidioidomycosis is caused by exposure to fungal spores. Coccidioidesspores become airborne when soil is disturbed by wind or digging, excavation, or other construction activity. The fungus can be present in soil 2 to 12 inches below the surface, usually in hot desert areas, and it’s endemic to parts of the southwestern United States, including parts of Arizona, California, New Mexico, Texas, and Utah, although its range may be expanding.

According to California’s Division of Occupational Safety and Health (Cal/OSHA), Valley Fever is highly endemic in Fresno, Kern, Kings, Madera, Merced, San Luis Obispo, and Tulare counties. A county is classified as highly endemic when there are at least 20 cases of Valley Fever per 100,000 persons per year.

Outdoor workers, especially construction workers, are at risk of Valley Fever infections.

In 2019, Cal/OSHA cited a construction company for serious health and safety violations after two of its employees contracted Valley Fever.

The company’s workers were exposed to fungal spores while using hand tools to dig trenches in Fresno, Kings, and Merced counties.

The workers had been assigned to dig trenches up to 5½ feet deep to gain access to gas pipelines for maintenance. Dust wasn’t controlled, and the workers didn’t wear any respiratory protection. Cal/OSHA was notified the workers had been hospitalized with cases of Valley Fever.

Cal/OSHA recommendations for worksites in areas where Valley Fever is endemic include:

  • Minimizing the area of soil disturbed;
  • Using water or appropriate soil stabilizers to reduce airborne dust;
  • Stabilizing piles of soil with a tarp or other methods;
  • Providing air-conditioned cabs for vehicles that generate heavy dust and making sure workers keep windows and vents closed;
  • Suspending work during heavy winds; and
  • Placing any on-site sleeping quarters, if provided, away from dust sources.

When dust can’t be controlled, employers should provide NIOSH-approved N95, N99, N100, P100, or high-efficiency particulate air (HEPA)-rated respiratory protection, according to Cal/OSHA.

In 2019, California passed a law requiring construction firms and other employers in 11 counties in the Central Valley region to train employees in Valley Fever risks and control measures. The application of the law could expand to other regions of the state if cases of Valley Fever rise in those regions. The law applies to employers in alteration, construction, construction maintenance, painting, removal, renovation, repairing, or wrecking of any fixed structure or its parts.

Employers in the Central Valley must offer initial and annual training for all employees engaged in work expected to involve exposure to substantial dust disturbance.

Training must cover the following:

  • What Valley Fever is and how it’s contracted;
  • Areas, environmental conditions, and types of work that pose a high risk of contracting Valley Fever;
  • Personal factors that put employees at higher risk of infection or disease development, including diabetes, a compromised immune system due to conditions such as human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS), having received an organ transplant, pregnancy, or taking immunosuppressant drugs such as corticosteroids or tumor necrosis factor inhibitors;
  • Personal and environmental exposure prevention methods such as avoiding contamination of drinks and food, good hygiene practices when clothing or skin is soiled by dust, water-based dust suppression, wet cleaning dusty equipment when feasible, wearing a respirator when exposure to dust can’t be avoided, and working upwind from dusty areas when feasible;
  • The importance of early detection, diagnosis, and treatment to prevent the disease from progressing because the effectiveness of medication is greatest in the early stages of the disease;
  • Recognizing common signs and symptoms of Valley Fever, including cough, fatigue, fever, headache, joint pain or muscle aches, rash on the upper body or legs, shortness of breath, and symptoms similar to influenza that linger longer than usual;
  • The importance of reporting symptoms to the employer and seeking prompt medical attention from a physician for appropriate diagnosis and treatment; and
  • Prognosis and common treatment for Valley Fever.

Employers covered by the law may provide Valley Fever training as a stand-alone program or incorporate it into their existing injury and illness prevention programs (IIPPs).

California health officials suspect prolonged droughts and decreased snowpack in the Sierra Nevada area led to the spread of Valley Fever to areas of the state beyond the Central Valley.

If Valley Fever becomes highly endemic in additional California counties, employers in those counties must provide training after the first year.

Valley Fever’s spread beyond the Southwest

For decades, Valley Fevercases were confined to the Southwest states of Arizona, California, Nevada, New Mexico, Texas, and Utah. Cases have been tracked in the Southwest since the 1930s and ’40s.

However, the range of areas where Coccidioidesis endemic has spread within the United States. For example, the CDC has reported an increase in cases in south-central Washington state since 2013.

Public health officials are concerned cases may pop up in other parts of the country. Alabama, Arkansas, Delaware, the District of Columbia, Indiana, Kansas, Louisiana, Maryland, Michigan, Minnesota, Missouri, Montana, Nebraska, New Hampshire, North Dakota, Ohio, Oregon, Rhode Island, South Dakota, Washington, Wisconsin, and Wyoming all have Valley Fever reporting requirements.

Federal researchers speculate that climate factors like drought may be widening the endemic range of Valley Fever. The National Oceanic and Atmospheric Administration (NOAA) has reported its research has shown that warming ocean waters have led to an increase in dust storm activity and Valley Fever infections.

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