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Glossary of terms



Aerosol - assembly of liquid or solid particles suspended in a gaseous medium

Air pollution - conditions of materials present in the air at levels detrimental to the health and/or welfare of human beings

Air quality - features of the air which have an impact on humans and/or the environment

Allergen - substance that can cause an allergic reaction in a sensitised person

Allergy - adverse health reaction upon secondary contact with the antigen

Allergic bronchopulmonary aspergillosis (ABPA) - pulmonary disorder caused by hypersensitivity to fungal antigens of Aspergillus genera, most often of A. fumigatus species




Bacteria - large group of prokaryotic microorganisms with one chromosome in a nuclear region and which only replicate asexually through cell division

Bioaerosol - particles of biological origin suspended in a gaseous medium (e.g. in the air)

Biological agent - one of a number of agents such as bacteria, viruses, fungi and other microorganisms or parts of them and their associated allergens or toxins, including those which have been genetically modified, cell cultures or endoparasites, which are potentially hazardous to human health

Breathing zone - space around the nose and mouth from which air is inhaled




Cascade impactor - sampler operating based on impaction principle that a series of impaction stages with decreasing particle cut-size so that particles can be separated into relatively narrow intervals of aerodynamic diameter

Colony forming unit (CFU) - number of biologically active particles (e.g. bacteria, fungi) that can form a single colony present in a unit of volume of the air

Culturable - biological entity able to form colonies on a solid nutrient medium




Deposition - transfer of an air pollutant to a surface due to gravity or another precipitation mechanism

Deoxyribonucleic acid (DNA) - macromolecular organic chemical compound belonging to nucleic acids; it is found in chromosomes and acts as a carrier of genetic information of living organisms

Dermal exposure - direct contact between a chemical or biological agent and human skin

Disinfection - process aimed at minimising the number of microorganisms with a chemical on inanimate objects




Endotoxin - constituent of the outer membrane of Gram-negative bacteria (lipopolysaccharide), consisting of a complex lipid, lipid A, which is covalently bound to a polysaccharide

Endotoxin unit (EU) - unit standardised against the defined reference material (reference standard endotoxin)

Enzyme-linked immunosorbent assay (ELISA) - assay in which an enzyme is linked to an antibody and a coloured substrate is used to measure the activity of bound enzyme and, hence, the amount of bound antibody




Filtration - collection of particles suspended in gas or liquid by flowing through a porous medium

Fungi - diverse group of eukaryotic microorganisms with membrane-bound nucleus comprising several chromosomes




Glucan - polysaccharide molecule present in the cell walls of eukaryotes and prokaryotes including most moulds, yeasts, algae, higher plants and certain bacteria

Glycoproteins - proteins containing, usually numerous, oligosaccharides (several saccharide units) covalently bound to them

Gram-negative - not retaining the primary stain (crystal violet) during the Gram staining procedure

Gram-positive - retaining the primary stain (crystal violet) during the Gram staining procedure




Impaction - collection of airborne particles accelerated through the nozzle or orifice on a surface by the inertia effect

Impingement - combination of impaction onto a surface and subsequent dispersion into a liquid medium

Incident - occurrence arising out of, or in the course of, work that could or does result in injury and ill health

Indoor air - air within an enclosed space, e.g., dwelling or public building

Inhalation exposure - situation in which a chemical agent or biological agent is present in the air that is inhaled by a person




Limulus amoebocyte lysate (LAL) - enzymes extracted from the blood cells of the horse shoe crab (Limulus polyphemus) that are activated by endotoxin and other molecules (e.g. glucans)

Lipopolysaccharide (LPS) - large molecule consisting of lipids and sugars joined by chemical bonds (see endotoxin)




Mesophilic microorganisms - microorganisms that can grow in the temperature range of 20–45°C, with optimal temperature between 30–37°C

Metabolite - product of metabolism (i.e. chemical changes taking place in organisms)

Microbiological culture - method of multiplying microbial organisms by letting them reproduce in a predetermined culture medium under controlled laboratory conditions

Microbial volatile organic compounds (MVOCs) - chemical compounds of low molecular weight, typically released by growing fungi and bacteria as end-products of their metabolism

Microbiota - complex of microorganisms present in a given habitat

Microorganism - microbiological entity of any type, cellular or non-cellular, capable of replication or of transferring genetic material, or entities that have lost these properties

Mould - microscopic fungus principally producing filaments; grow in the form of hyphae and form a dense mass, called mycelium; asexual spores (conidia) can be easily released into the air

Mycotoxins - toxic secondary metabolites produced by fungi




Occupational exposure - exposure to potentially harmful chemical, physical or biological agents that occurs as a result of one’s occupation

Occupational health and safety policy - policy to prevent work-related injury and ill health to workers and to provide safe and healthy workplaces

Organic Dust Toxic Syndrome (ODTS) - illness occurs as a result of exposure to high levels of microbial agents contained in organic dust




Peptidoglycan - polymer that is composed of polysaccharide and peptide chains and is found in bacterial cell walls and some other organisms

Polymerase Chain Reaction (PCR) - key technique in molecular genetics that permits the analysis of any short sequence of DNA (or RNA) without having to clone it; used to reproduce (amplify) selected sections of nucleic acid




Respirable fraction - fraction of inhaled particles that can reach the gas exchange region of the human respiratory tract

Risk - measure of the probability and severity of an adverse effect on life, health, property or the environment

Risk analysis - the use of available information to estimate the risk to individuals or populations, property or the environment, from hazards

Risk assessment - process of making a decision recommending whether or not existing risks are tolerable and present risk control measures are adequate, and if not, whether alternative risk control measures are justified or will be implemented




Sick building syndrome (SBS) - set of adverse symptoms connected with bad quality of indoor air when no specific cause and/or disease could be identified




Thermophilic microorganisms - microorganisms that can grow in the temperature range 30–90°C, with an optimal temperature of 50–70°C




Vaccine - preparation of killed, living attenuated or living fully virulent (micro)organisms that are administered to produce or artificially increase immunity to a particular disease

Ventilation - air exchange or circulation of the air; system or means of providing fresh air

Viable microorganisms - microorganisms having a potential for metabolic activity




Worker - person performing work or work-related activities that are under control of the organization

Workplace air - air to which a person is exposed, whether indoor or outdoor, during the hours of work at the person's workplace




Yeast - fungi, usually single-celled, that reproduce sexually or asexually by budding; under unfavourable conditions for vegetation, they form spores as dormant structures




Zoonosis - disease transmitted from animals to humans