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L'Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST, Occupational Health and Safety Research Institute Robert Sauvé) is a scientific research agency committed to the identification

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L'Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST, Occupational Health and Safety Research Institute Robert Sauvé) is a scientific research agency committed to the identification and elimination at the source of occupational hazards, and the rehabilitation of workers who have suffered occupational injuries. With funding provided by the Commission pour la santé et la sécurité au travail du Québec (CSST, Québec Occupational Health and Safety Commission), the IRSST conducts, funds and contracts research aimed at reducing the human and financial costs of occupational accidents and diseases. For up-to-date information on research conducted or funded by the IRSST, subscribe to Prévention au travail, the free magazine published in conjunction with the CSST. Legal Deposit Bibliothèque nationale du Québec 2001 IRSST - Direction des communications 505, boul. de Maisonneuve Ouest Montréal (Québec) H3A 3C2 Telephone: (514) Télécopieur: (514) Institut de recherche en santé et en sécurité du travail du Québec, November 2001. i TABLE OF CONTENTS CONTEXT... 1 NOTICE TO THE READER... 2 SECTION 1: GENERAL INFORMATION Knowledge about microorganisms Bacteria Molds and yeasts Metabolites, toxins or fragments of microorganisms Other microorganisms... 8 References cited and bibliography Bioaerosol concentrations measured in the workplace References cited and bibliography Exposure values References cited and bibliography SECTION 2: EVALUATION STRATEGY General evaluation procedure Evaluation methods Evaluation of the work environment Detailed inspection of a building Methods for measuring bioaerosols Sampling plan Interpretation and communication of results Examples References cited and bibliography SECTION 3: CONTROL OF BIOAEROSOL EXPOSURE Industrial work environments Non-industrial workplaces References cited and bibliography ANNEX 1 : PHOTOS OF MOULDS ANNEX 2 : TECHNICAL SHEETS FOR THE CONTROL OF BIOAEROSOL EXPOSURE ANNEX 3 : Miscellaneous envelope details... 83 ii LIST OF TABLES Table 1: Main bioaerosols potentially present in the air Table 2: Dominant bioaerosols in relation to substrates Table 3: Bioaerosol concentrations measured in workplaces Table 4: Endotoxin concentrations measured in workplaces Table 5: Action criteria proposed by the IRSST Table 6: Bioaerosol sampling techniques regularly used at the IRSST Table 7: Number of samples (ACGIH, 1999) Table 8: Fungal abatement protocol (NYCDH, 2000) LIST OF FIGURES Figure 1: Bacteria found in 63 work environments Figure 2: Molds found in 126 work environments Figure 3: General procedure for evaluating workplace exposure to bioaerosols... 27 1 CONTEXT Microorganisms are ubiquitous in our environment: they are present in water, soil, air, plants, animals and people. In the workplace, the interest in microorganisms mainly relates to their presence in the air; they are then called bioaerosols. Bioaerosols are defined as airborne particles consisting of living organisms such as microorganisms or originating from living organisms, such as metabolites, toxins or fragments of microorganisms. For the majority of them, the dose/effect relationships by inhalation have not been established, but the scientific community nevertheless agrees that some bioaerosols may cause health problems. The international interest in bioaerosols as an agent that can affect workplace air quality and workers health has rapidly increased the pool of knowledge on their identification, quantification, their presence in different workplaces, and the effects that they can produce in the people exposed to them. Different approaches for risk evaluation are used by occupational health researchers and professionals, which raises questions mainly about the types of microorganisms or derivatives to be investigated; the purpose, techniques and locations of sampling; result interpretation, taking into account the lack of exposure standards and dose/effect relationships, and the most effective means for correcting an abnormal situation or for maintaining healthy conditions. This practical guide describes the approach recommended by the IRSST for the evaluation, control and prevention of bioaerosol exposure; it corresponds to the typical industrial hygiene procedure, namely the anticipation, identification and evaluation of the risks, with the ultimate purpose of controlling exposures in order to prevent disease. The guide is divided into three sections. The first section synthesizes the most current information on the types of bioaerosols present in workplaces, their natural environment, and the conditions conducive to their growth and proliferation. The effects on health of the different bioaerosols are presented in a brief and general way, since this aspect of the procedure must always be entrusted to a physician. It also includes information on the concentrations measured in different workplaces and the proposed exposure values. The second section covers the strategies for evaluating a workplace based on the objective pursued. The methods, techniques and tools available for this evaluation, the sampling plan, and result interpretation are addressed. The third section presents means of control and prevention. The specific case of the demolition and repair of water-damaged materials is considered. For each of the chapters, the consulted references are listed, as well as those that may serve as complementary tools. The aim of this guide is to harmonize the evaluation and prevention approach for bioaerosol exposure through a better understanding of the possibilities and limits of the procedure applied. This procedure applies to all activity sectors where bioaerosols can be present in abnormal concentrations. 2 NOTICE TO THE READER Since microorganisms are ubiquitous in the environment, bioaerosol exposure in unavoidable. In this document, the expressions potential exposure to bioaerosols or exposure to bioaerosols refer to a situation in which the bioaerosol concentrations are abnormally high. 3 SECTION 1: GENERAL INFORMATION 1.1 Knowledge about microorganisms Microorganisms are ubiquitous in our environment: they are present in water, soil, air, plants, animal and humans. The interest of an industrial hygiene viewpoint mainly relates to the bioaerosols or microorganisms in the air, and more specifically the bacteria, molds and yeasts and their metabolites, toxins or fragments. Other microorganisms are occasionally associated with air quality and are considered briefly in this document; these are dust mites or acarids and viruses. The majority of bioaerosols are of respirable size, namely in the order of µm for viruses, from 0.5 to 20 µm for bacteria, from 10 to 100 µm for plant pollens, and from 2 to 200 µm for molds. The health effects reported here are of a comprehensive and general nature since this aspect of the process must always be entrusted to a physician. A scientific advisory from the ministère de la Santé et des Services sociaux du Québec (Québec ministry of health and social services) dealing with exposure to molds in the indoor environment is being prepared and will be a reference document for health effects and medical investigation tools. Additional information can be found in the references mentioned at the end of this section Bacteria Bacteria are abundant in the environment and in humans. There are more than 150,000 known species of bacteria. They are single-celled organisms that reproduce by simple cell division. The majority of bacteria contain the necessary genetic information and energy capacity to ensure their growth and reproduction. They are capable of using various inorganic and organic nutrient sources. The majority of the species encountered in air quality are saprophytes, meaning that they get their energy from organic sources. Bacteria are classified on the basis of cellular, morphological or biochemical characteristics. They are divided into two major groups based on their reaction to Gram stain: Gram positive bacteria and Gram negative bacteria. Bacteria require a lot of moisture to multiply. Gram negative bacteria have a fragile cell wall that does not tolerate well the dehydration that they undergo when exposed to air for prolonged periods or during sampling. Gram positive bacteria have a more resistant wall, and some produce spores that give them an increased resistance to variations in environmental conditions. This group contains thermophilic bacteria, bacteria whose growth is promoted at higher temperatures and that are of particular interest in air quality. In the outdoor environment, bacteria mainly come from water, soil and plants and are associated with the presence of humans and animals. Bodies of water can dissipate bacteria into the air by aerosolization, just like the emissions from certain industrial processes and cooling units. Inside non-industrial buildings, bacteria come mainly from the occupants because bacteria make up the natural flora of the skin and mucous membranes. Indoors, the species are more numerous and the concentrations are above those of the outdoor environment. Some workplaces such as barns, breeding farms, waste and wastewater treatment plants, and food and beverage plants are themselves conducive to the presence and growth of bacteria. This type of environment is where Gram negative bacteria are more likely to be measured. 4 The majority of bacteria naturally present do not cause adverse health effects. Some bacteria are even essential to both the human body and the environment. Health risks appear when the concentrations of some species become abnormally high. High concentrations of thermoactinomycetes bacteria may cause hypersensitivity pneumonitis such as farmer s lung. Some bacteria are recognized as the agents responsible for infectious diseases. The health risk related to the presence of Legionella pneumophila bacteria, namely legionnaire s disease, is well documented. There are two distinct types of legionellosis, namely legionnaire s disease, a progressive pneumonia that can be fatal, and Pontiac fever causing symptoms similar to those of influenza. This bacterium is known for its ability to develop in water tanks. It is prone to drying and does not survive outside water. However, it can be transmitted through the air by the projection of the droplets of water that contain it. The genus Mycobacterium is also of health interest, and particularly the species Mycobacterium tuberculosis, the etiologic agent responsible for tuberculosis. The majority of species of mycobacteria live in soil and water but their main niche is the unhealthy tissues of warm-blooded animals, including humans. The Mycobacterium tuberculosis bacterium is airborne by droplets generated by carriers of the disease and by ventilation systems. People who have persistent health problems that seem to be related to exposure to bacteria or other bioaerosols must consult a physician. Table 1 reports the main types of bacteria that are potentially present in workplace air according to the literature. Figure 1 shows the prevalence of the different types identified by the IRSST s microbiology laboratory in 63 work environments, including 36 office buildings, 12 schools and 15 hospitals, originating from requests for analyses that it has received in the last 8 years. Molds and yeasts There are currently several tens of thousands of known species of molds and yeasts, with the two groups being in the fungus family. Fungi are ubiquitous in the environment and are primary saprophytes, meaning that they use dead organic material as a source of nutrients for their growth and reproduction. Several live in the soil and take an active part in the decomposition of organic material. They are generally aerobic. Humans may be commonly exposed to more than 200 species of them, several of which proliferate well in a humid indoor environment. Yeasts are single-cell organisms that divide by fission and budding. Molds are multicelled and they propagate by spores. These components develop into filaments called hyphae, which, by clumping, form the mycelium. This produces a more specialized structure, the spore apparatus, responsible for the formation of spores. Spores differ in form, size and color. They can survive from a few days to several years. Each spore that germinates may produce a new mold, which in turn, under the appropriate growing conditions, may produce millions of spores. Molds release their spores under the effect of major air currents or as a reaction to unfavorable conditions such as a rapid increase or decrease in humidity or to reach a new source of food. The presence of these spores in the air also depends on their mode of dispersion. In fact, the mode of dispersion and transfer for spores differs with the species. Some spores, called gloeiospores, have a thick wall of moist consistency and remain stuck together by mucus. They form heavy bodies that are not easily transported by the air. They are carried by substrates by contact, insects or water. This is the case for molds of the genera Acremonium and Exophiala. Other genera such as Penicillium and Cladosporium have spores with dry walls, easily dissociable and light. They are more easily dispersed in the air. Spore concentrations in the air depend on the surrounding conditions and therefore vary during any given day. In nature, the concentration of molds has its peak from July to the end of the fall. Contrary to pollens, molds persist after the first frost. A few may develop at temperatures below the freezing point but most become dormant. Snow cover drastically reduces the concentrations in the air but does not kill molds. When the snow melts, molds develop on the dead vegetation. Temperature affects the rate of growth of molds. They have a minimum, maximum and optimal growth temperature. The ambient temperature in the order of 20 to 25 0 C maintained in the majority of indoor environments corresponds to an ideal growth zone for the majority of them. The main genera of molds and yeasts potentially present in workplace air according to the literature are listed in table 1. Figure 2 shows the prevalence of the different genera identified by the IRSST microbiology laboratory in 126 work environments including 47 office buildings, 41 schools, 23 hospitals and 15 plants. These data originate from requests for analyses sent to the laboratory in the last 8 years. This distribution agrees with those reported in the literature (Thorne and Heederick, 1999; Nolar, 1999). Photographs of molds are given for information purposes in Appendix 1. Yeasts and molds can therefore be found everywhere there is an appropriate temperature, humidity, oxygen, sources of carbon and nitrogen and the minerals that they need. Their 6 biological activities of biodegradation or biodeterioration depend on their own enzymatic activities, the environmental conditions, the phenomenon of competition, and the nature of the substrate. For example, some molds easily use cellulose, and their proliferation is favored when the materials containing it are soaked with water. Table 2 lists the main genera of molds that can develop on different substrates. To date, epidemiological studies have not established a causal relationship between the extent of the fungal presence, exposure to the molds in the air and specific health effects, or the frequency and severity of the symptoms reported. Studies tend to demonstrate the existence of relationship between mold exposure and the development of some symptoms, particularly respiratory symptoms. Several of these studies have also noted the presence of high humidity. It can therefore be difficult to separate the effects of high humidity from those of the molds. For the majority of people, ambient concentrations of molds do not cause health effects. However, in situations where the concentrations are abnormally high or for certain people suffering from respiratory problems or whose immune systems are deficient, exposure to molds may promote the appearance of symptoms and illness. The effects felt depend on the species present, their metabolic products produced, the concentration, and duration of exposure, and individual susceptibility. The nature of the dose-response relationship between exposure to molds and the impact on health is not known, no more than a safe exposure threshold below which there is no risk. The main health effects associated with exposure to molds are hypersensitivity reactions (allergy), infections and irritation. Hypersensitivity reactions Allergy is the most common manifestation associated with exposure to molds. Most produce antigenic proteins that may cause an allergic reaction in sensitized people, including asthma, rhinitis and conjunctivitis. Hypersensitivity pneumonitis may also occur. However, several authors associate exposure to low levels of molds with an exacerbation of asthma and other respiratory problems. 7 Infections Some one hundred species are known to cause infection in people. There are three classes of infections caused by molds: systemic, opportunistic and superficial. Systemic infections such as histoplasmosis (due to the mold Histoplasma capsulatum found mainly in bird droppings) are caused by the inhalation of spores. Opportunistic infections are generally limited to people whose immune systems are deficient. The main molds responsible for these opportunistic infections are Aspergillus, Acremonium, Beauvaria, Cladosporium, Fusarium, Mucor, Paecilomyces, Penicillium, Rhizopus, Scedosporium, Scopulariosis and Trichoderma. Dermatophytes are a group of molds that affect the scalp, skin and nails. These infections occur by skin contact. Transmission to humans through the air is very unlikely. Irritation Metabolism of molds produces volatile organic compounds that cause the musty smell associated with fungal growth. The following compounds have been identified as indicators of microbial growth: 1-octene-3-ol, 2-octene-1-ol, 3-methyl furan, 3-methyl-2-butanol, 3-methyl-1- butanol, 2-pentanol, 2-hexanone, 2-heptanone, 3-octanone, 3-octanol, 2-methyl-isoborneol, 2- methyl-2-butanol, 2-isopropyl-3-methoxypyrazine, geosmine. These compounds can be irritating to the mucous membranes. Individuals who have persistent health problems that seem related to exposure to molds or other bioaerosols must consult a physician. The physical examination and patient s history may lead to the clinical diagnosis. Few complementary clinical tests are available, except in cases of allergy. Immunological tests such as skin tests are used to detect specific antibodies. Measurement of the antibodies developed by a person following exposure only means that there was exposure without determining its extent or duration. Considering the pervasiveness of molds and therefore exposure, this measurement is of limited usefulness. Respiratory function and respiratory provocative challenge tests are also used to help in the diagnosis Metabolites, toxins or fragments of microorganisms Mycotoxins During the nutrient degradation process, molds release secondary metabolites called mycotoxins that they use as a defense against other microorganisms including other molds. A given fungal species may produce different toxins depending on the substrate and the local environmental factors. Mycotoxins are nonvolatile compounds and will be found in the air only if the environment in which they are produced is disturbed. The health effects from respiratory exposure to mycotoxins are not well known. They could be the causal agents of the effects reported following exposure to molds. The reported symptoms vary with the type, nature and extent of contact. They include: skin and mucous membrane 8 irritation, immunosuppression, and systemic effects such as dizziness, nausea, headache, and cognitive and neuropsychological effects. It should be noted that the latter effects are not extensively documented
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