Fungal Composition of Air and Pollution in Southern New Mexico

Respiratory illnesses have been attributed to poor air quality both outdoors and in the home. As part of our research on border air quality, members of the team have looked into the presence of bioaerosols in the air. Bioaerosols include pollen, viruses, bacteria, dust mite feces, and microbes such as fungal spores. The Clean Air Act mandates monitoring of a number of gas and aerosol pollutants that have been studied and shown to have causal relationships between human health and concentrations. Bioaerosols are not routinely monitored by state, local, and tribal agencies though they have been attributed to respiratory diseases such as asthma. For this reason, our study is critical. In this study, we took dry and wet samples from various places along the border, including near dairies in Dona Ana county, inactive cattle yards in Columbus/Palomas, two open are construction sites in Las Cruces, two residential sites in Las Cruces, and on the NMSU main campus. The full report on the study and a poster presented at the 2013 American Meteorological Society's Annual Meeting are available below.

Study Objective

The objective of this study is to acquire a database of environmental conditions in and around the study area that are relevant to studies of soil fungi. Samples were collected near the surface near suspected dust sources and during high dust loading events.

Samples Collected

We collected fungal species in both dry and wet deposition samples over the spring, summer, and fall of 2012. For dry deposition samples we used both passive and active sampling methods. The passive method used agar plates exposed for 2 hours to ambient air at a height of 1-meter above the ground. We also used SKC a Biostage and Anderson cascade impactor for collecting particles in several micron-sized categories. We deposition samples were collected using zip lock bags inserted in 4-inch CoCoRaHS rain gauges. In the laboratory we monitored Petri plates for fungal growth and enumerated fungal colonies. We then catalogued and enumerated each fungal colony based on color, growth pattern, and texture. We characterized each colony type by molecular method through PCR and examined each colony type by microscopy.

Map of all sampling locations during study
Map of all sampling locations during the study

Variations in Fungal Species

Over all sites, the total number of fungi varied from 7 to over 167, as shown below. The sample with the most number of fungi present was from the NMSU on May 21, 2012 during the thunderstorm outflow. Interestingly, several samples with the relatively highest number of fungal colonies are during thunderstorms. Samples that were collected at or near a cattle yard or dairy are shown in the figure as cross hatched.

Bar graph of fungi totals

Fungal genera or species identified so far include Alternaria, Alternaria alternata, Alternaria arborescens isolate, Alternaria brassicae, Alternaria porri, Aspergillus fumiagtus, Aspergillus niger, Aureobasidium pollulans, Biploaris spicifera, Cladosporium, Cladosporium cladosporioides, Dothideomycetes sp, Dreschlera, Epicoccum, Epicoccum sp, Fusarium, Fusarium oxysporum, Nigrosporum, Penicillium, Peyronellaea glomerata, Rhizopus, Stemphylium solani, and Trichoderma. Of these fungal microorganisms, many have been reported to be associated with medical conditions. For example, Aureobasidium, a fungus with yeast-like growth known for its allergenic properties (asthma and hay fever), may become an opportunistic pathogenic microorganism associated with health issues such as pulmonary mycosis. Similarly, other fungal microorganisms such as Aspergillus niger and Aspergillus fumigatus are also associated with medical conditions including aspergillosis.

Findings

We collected 23 different fungal species as part of our fungal taxonomy database for the region. Samples were taken at diverse locations including dairies in Mesilla Valley, along the border at Columbus/Palomas port of entry, two suburban locations in Las Cruces and El Paso, at two construction sites in Las Cruces, on the campus of NMSU, and a background site at the top of Sandia Peak at 10,000 feet. Fungal abundance in rainfall varied by over four orders of magnitude over all samples.

One pair of samples collected near dairy dust sources showing diversity and spatial variation within 2 km.

Implications

Of these fungal microorganisms, many have been reported to be associated with medical conditions. For example, Aureobasidium, a fungus with yeast-like growth known for its allergenic properties (asthma and hay fever), may become an opportunistic pathogenic microorganism associated with health issues such as pulmonary mycosis. Similarly, other fungal microorganisms such as Aspergillus niger and Aspergillus fumigatus are also associated with medical conditions including aspergillosis.

Fungi and Health Effects

Release of Fungi in the Atmosphere

Dry spores from fungi such as Alternaria, Aspergillus, Cladosporium and Penicillium species are mostly emitted in dry, warm and windy conditions. The minimum wind speed required for detachment varies from 0.5 m/s for Aspergillus and Penicillium species to 1.0 m/s for Cladosporium species. Once airborne, the spores are easily dispersed and can be transported for long distances by the wind.

Health Effects of Aspergillus Fumigatus and Aspergillus Niger

Exposure to Aspergillus has been shown to exacerbate symptoms of asthma and allergic rhinitis. Allergic bronchopulmonary aspergillosis (ABPA) is caused by Aspergillus fumigatus and is characterized by exacerbations of asthma, recurrent transient chest radiographic infiltrates, coughing up thick mucus plugs, peripheral and pulmonary eosinophilia, and increased total serum IgE and fungus-specific IgE levels, especially during exacerbation (IgE is immunoglobulin E, an antibody). The airways appear to be chronically or intermittently colonized by Aspergillus fumigatus in patients with ABPA. ABPA is the most common form of allergic bronchopulmonary mycosis (ABPM). The characteristics of ABPM included severe asthma, blood and pulmonary eosinophilia, markedly increased IgE and specific IgE levels. Case-fatality rates (CFRs) were 99%, 86%, and 66% for cerebral, pulmonary, and sinus aspergillosis, respectively. Aflatoxin from Aspergillus is capable of causing liver cancer while Ochratoxin-A is a possible human carcinogen. Exposure to aflatoxin and ochratoxin occurs by ingestion, but can also occur by inhalation in industries such as peanut processing, livestock feed processing, or when grain dust exposure occurs. Papers that have more information about the health impacts of Aspergillus that are available online are listed below. A full listing of papers can be found in the final report on the study linked above.

  1. IgE Sensitization to Aspergillus Fumigatus is Associated with Reduced Lung Function In Asthma. Fairs et al. (2010).
  2. Aspergillosis Case-Fatality Rate: Systematic Review of the Literature. Lin et al. (2001).

Health Effects of Penicillium

Exposure to Penicillium has been shown to exacerbate symptoms of asthma and allergic rhinitis in sensitive individuals. Children who were exposed to detectable levels of Penicillium were twice as likely to experience increased days of wheeze, persistent cough and a higher asthma severity score than children who were unexposed. Indoor Penicillium species levels correlated with peak expiratory flow rate variability in asthmatic children. Penicillium shows no seasonal variability and it can survive in house dust for 5 years.

A paper that contains information on the health impacts of Penicillium that is available online is listed below. A full list is available in the final report on the study linked above.

  1. Household Airborne Penicillium Associated with Peak Expiratory Flow Variability in Asthmatic Children. Bundy et al. (2009).

Health Effects of Cladosporium Cladosporioides

Fungal sensitivity, particularly to Cladosporium species, increases the risk of adult-onset asthma. Exposures to Cladosporium were also associated with hypersensitivity pneumonitis Outdoor counts tend to be higher in warmer weather and during thunderstorms.

A paper containing more information on the health impacts of Cladosporium that is available online can be found below. A full list of papers can be found in final report on the study linked above.

  1. Cladosporium Species-Related Hypersensitivity Pneumonitis in Household Environments.

Health Effects of Alternaria Alterante

Alternaria species is a predominant outdoor fungus but has been reported in house dust samples. Alternaria species exhibits diurnal periodicity, with counts peaking during daylight hours. Sporulation is induced by light rain or heavy dew, with sudden humidity changes stimulating release. The National Health and Nutrition Examination Survey III study reported that 12.9% of US citizens aged 6 to 59 years have positive skin prick test (SPT) responses to Alternaria species. Exposure to Alternaria has been shown to exacerbate symptoms of asthma and allergic rhinitis in sensitive individuals. Exposure to Altenaria alternata antigens correlated with active asthma symptoms, persistent adult asthma (odds ratio, 7.4) and potentially fatal episodes of asthma. Epidemics of asthma caused by increased airborne Alternaria spores that occur during thunderstorms further illustrate this association.

Papers that have more information about the health impacts of Alternaria that are available online are listed below. A full list of papers is included in the the final report on the study linked above.

  1. Exposure to Alternaria Alternata in US Homes is Associated with Asthma Symptoms. Salo et al. (2006).
  2. The Role of Fungal Spores in Thunderstorm Asthma. Dales et al. (2003).

Health Effects of Aureobasidium Pullulans

Sensitivity to Aureobasidium pullulans was associated with severity of asthma (odds ratio of 1.4) for severe vs mild and moderate asthma. It is also associated with an outbreak of extrinsic allergic alveolitis.

Health Effects of Drechslera

Sensitivity to Drechslera-type spores (including Bipolaris, Drechslera, Exserohilum, and Helminthosporium), is significant (around 26%) in Finnish asthmatic children. Drechslera is detected in less than 10% of mold-contaminated southern California buildings. Drechslera Ito was significantly associated with Kashin-Beck disease (KBD) is a chronic, endemic osteochondropathy (disease of the bone), which is mainly observed in northeastern to southwestern China.

Papers that discuss the health impacts of Drechslera that can be found online are listed below. A more complete list can found in the final report on the study linked above.

  1. A Regional Comparison of Mold Spore Concentrations Outdoors and Inside "Clean" and "Mold Contaminated" Southern California Buildings. Baxter et al. (2005).
  2. A 4-year Study of the Mycological Aspects of Kashin-Beck Disease in Tibet. Chasseur et al. (2001).

Health Effects of Fusarium

Fumonisins, fungal toxins produced by Fusarium moniliforme, contaminate maize based foods and feeds throughout the world (Turner et al., 1999). They cause liver and kidney toxicity in animals in addition to leukoencephalomalacia in horses and pulmonary edema in pigs that are shown to be toxic in animal models (Pestka, 2010). Chronic exposure to Fusarium-produces deoxynivalenol (DON), nivalenol (NIV) and their acetylated precursors at low doses causes growth retardation and immunotoxicity whereas much higher doses can interfere with reproduction and development (Sudakin 2003; Wilkins et al., 2003).

Papers that have more information on Fusarium that are available online are listed below. A more complete listing can be found in the final report on the study linked above.

  1. Trichothecenes In the Environment: Relevance to Human Health. Sudakin (2003).
  2. Patterns of Volatile Metabolites and Nonvolatile Trichothecenes Produced by Isolates of Stachybotrys, Fusarium, Trichoderma, Trichothecium and Memnoniella. Wilkins et al. (2003).
  3. Fumonisin Contamination of Food. Progress in Development of Biomarkers to Better Assess Human Health Risks. Turner et al. (1999).

Health Effects of Nigrospora

There are no studies showing associations of nigrospora with adverse human health effects.

Health Effects of Rhizopus

Rhizopus species account for less than 3% of total airborne spores. Rhizopus nigricans are found to be associated with occupational respiratory diseases such as hypersensitivity pneumonitis in malt worker's lung, wood trimmer's disease and coal miners (Belin 1985; Gamboa et al., 1996).

A paper that has more information on the health impacts of Rhizopus that is available online is listed below.

  1. Occupational Asthma In A Coal Miner. Gamboa et al. (1996).

Health Effects of Stemphylium Solani

There are no studies showing associations of Stemphylium solani with adverse human health effects.

Health Effects of Trichoderma

Exposure to Trichoderma species has been shown to exacerbate symptoms of asthma and allergic rhinitis. Allergic fungal sinusitis is also triggered by exposures to Trichoderma longibrachiatum in a patient with a history of atopy and asthma (Beezhold et al., 2008; Tang et al., 2003).

A paper that has more information about Trichoderma that is available online is listed below. A more complete list is included in the final report on the study linked above.

  1. Allergic Fungal Sinusitis Associated with Trichoderma Longibrachiatum. Tang et al. (2003).

Next Steps and Recommendations

While the majority of the past samples used passive techniques with the particles settling on the media with natural winds, future methods are to collect size segregated or separated samples that are inhalable using impactors. We used the impactors at the end of the growing season in 2012 and intend to resume this in 2013. Other sampling methods on filter media and microscope slides are being tried as part of the project. We will be investigating to see if any of those samples can be cultured for fungal species.

As we continue to collect samples in the remaining part of fiscal year 2013 it will be informative to see differences in number and species between the low wind samples compared to the ones during the thunderstorms over the spring of 2013 and following year. We intend to take more high wind spring samples in 2013 using standard plates and impactors.