Biological agents

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Ioannis Basinas. Institute of Occupational Medicine, Edinburgh

Introduction

Biological agents have a ubiquitous presence in the environment and are found in many sectors. As they are rarely visible, the risks they pose are not always appreciated, but exposure may lead to include acute and chronic, sometimes life-threatening, diseases with serious socio-economical consequences. Health effects include infections, zoonotic diseases, symptoms of the upper and lower respiratory tract, occupational asthma, sensitisation, allergic reactions, systemic (multi-organ) effects, poisoning and cancers.

Risk assessment and management of biological agents in workplaces is a legal requirement, but the process may be complicated because of the diversity of such agents, as they have unique properties which differentiate them from other dangerous substances. These include infectiousness, delayed effects through incubation, and an ability for self-multiplication . There is a lack of standardised measurement methods and there are generally no established occupational exposure limits for biological agents.

This article gives a general overview of the sources and occurrence of exposure to biological agents in workplaces, and of the health effects of such exposures. Furthermore, it introduces the currently available legislation, and discusses general measures that may be applied to control and prevent exposure for these agents in the workplace.

Definition

In 2000 the European Parliament and Council published Directive 2000/54/EC “on the on the protection of workers from risks related to exposure to biological agents at work” that adopts a strict definition of biological agents[1]. Specifically, in Article 2 of the directive, biological agents are defined as the “micro-organisms, including those which have been genetically modified, cell cultures and human endoparasites, which may be able to provoke any infection, allergy or toxicity”. Micro-organisms are defined as microbiological entities, cellular or non-cellular, capable of replication or of transferring genetic material.

Beyond this formal legal definition they may also be classified as a group of substances comprising of micro-organisms such as viruses and zoonoses, parasites, bacteria, and fungi; their by-products including toxins, constituents of their cell-walls (e.g. endotoxins and glucans); and parts of living organisms.

Wider definition in some Member states

A detailed examination of all 24 OSH Directives found no major discrepancies in the implementation of the Biological Agents Directive into national law. However, the Directives establish minimum standards for OSH and it remains open to individual member states to adopt more stringent requirements or standards. In the context of the definition of ‘biological agent’ for example, while some countries (e.g. Ireland[2]) have adopted the same definition as that included in the Directive, others have widened it. For example, the definition adopted in Germany includes ectoparasites, which are able to provoke any infection, allergy or toxicity, and technically produced biological entities with the same properties as biological agents[3] while, in the UK, the scope of action of such agents is extended to include ‘which may cause infection, allergy, toxicity or otherwise create a hazard to human health[4].

Because of national differences in definition it is important for any reader to refer to the relevant national regulations related to biological agents in workplaces.

The Biological Agents Directive (2000/54/EC) classifies biological agents into four risk categories according to their potential to cause diseases and the possibilities of prevention and treatment.[5] [6]

  • Group 1 biological agent means one that is unlikely to cause human disease;
  • Group 2 biological agent means one that can cause human disease and might be a hazard to workers; it is unlikely to spread to the community; there is usually effective prophylaxis or treatment available;
  • Group 3 biological agent means one that can cause severe human disease and present a serious hazard to workers; it may present a risk of spreading to the community, but there is usually effective prophylaxis or treatment available;
  • Group 4 biological agent means one that causes severe human disease and is a serious hazard to workers; it may present a high risk of spreading to the community; there is usually no effective prophylaxis or treatment available.

The Directive also includes as an annex a list of biological agents which are known to infect humans. The agents listed are classified in accordance with the four groups defined above. The list also provides indications of allergenic potential and toxic effects.

An alternative classification groups the agents according to their impact:

  • Agents of allergenic and toxic nature that form bioaerosols and are harmful for the respiratory tract, eyes and/or skin of humans. Important agents in this group include viruses, bacteria and fungi and their integral constituents’ endotoxins, β-glucans, chitin as well as plant particles, pollen and protein sensitizers.
  • Agents that cause infectious and parasitic diseases through one or more routes of transmission including disease vectors like insects and plants, direct or indirect physical contact (i.e. dermal exposure), air inhalation and or ingestion. Examples of agents belonging to this group include the zoonotic pathogens Methicillin-resistant Staphylococcus aureus (MRSA), Coxiella burnetti (causative agent of Q-fever), and Bacillus anthracis (anthrax) and the non-zoonotic bacterium Legionella sp[7].

Health effects

Biological agents can cause a broad range of adverse health effects, including:

  • infections caused by parasites, viruses, fungi or bacteria;
  • allergies, and acute as well as chronic respiratory symptoms triggered by exposure to mould and organic dusts like flour dust, animal dander, enzymes and mites;
  • poisoning or other toxic effects (for example through endotoxins).

Some biological agents including viruses (e.g. Hepatitis C, Human Immunodeficiency Virus-1), parasites (e.g. Schistosoma haematobium) and certain bio-aerosol contaminated dusts (e.g. wood dusts) are classified as carcinogenic to humans (Group 1) by IARC[8] [9] [10].

Biological agents can enter the human body via different routes depending on the agent and nature of the involved process. These may include entry through:

  • damaged skin or mucous membranes;
  • inhalation;
  • swallowing;
  • animal bites;
  • the uro-genital tract;
  • needle stick injuries, stings and cuts.

Workplace exposures

Biological agents have a ubiquitous presence in the environment and in occupational settings exposure can generally occur whenever workers come in contact with:

  • natural or organic materials like soil, clay, plant materials (hay, straw, cotton, etc.);
  • animals and substances of animal origin (e.g. wool, hair, etc.);
  • food (e.g. products, moulds & yeasts);
  • organic dust (e.g. flour, paper dust, animal dander, pollen);
  • waste, wastewater;
  • blood and other body fluids.

A considerable proportion of the global workforce is exposed to biological agents in either an intentional (i.e. when use of biological agents is deliberate) or unintentional/incidental manner. Workplaces with an increased potential for exposure to biological agents include those in primary agriculture, food processing, wood processing, health care, biofuel power plants, waste treatment, and research.[1, 3–5] An example list of sectors where occupational exposure to biological agents may occur is presented in Table 1, alongside the main biological agents of concern for each sector.

Table 1. List of indicative sectors and examples of relevant biological agents to which exposure may occur.   

Industry sector

Main biological agents of concern

Primary agriculture, animal feed production, veterinary service

Allergens (e.g. pollen, plant material and animal proteins from urine, hair and skin), mites, fungi (e.g. Aspergillus spp, Penicillium spp, dermatophytes) and bacteria (e.g. Actinomycetes, Brucella spp, Bacillus anthracis, Coxiella burnetii, Salmonella spp, MRSA, E.coli), and their cell-wall constituents (i.e. endotoxins and glucans), zoonotic viruses (e.g. Rabies, Influenza), parasites and ticks.

Health care, hospitals

Infectious agents including viruses (e.g. Hepatitis, human immunodeficiency viruses, rubella, Rabies, influenza), bacteria (e.g. Staphylococcus aureus, Streptococcus pyogenes, Mycobacterium tuberculosis, Legionella, Clostridium), fungi (e.g. Tinea spp, Aspergillus spp), parasites (e.g. Giardia lamblia) and prions. 

Laboratories

Infectious agents including zoononotic agents (e.g. Trichophyron spp, Toxoplasma gondii, Rabies), parasites (e.g. Leismania spp) and prions Allergens (e.g. from mites, plant material and animal proteins from urine, hair and skin).

Food and beverage production, bakeries

Fungi (moulds and yeasts), bacteria, and mites

Mycotoxins,  endotoxins, glucans, allergens including plant and animal proteins, enzymes (e.g. α-amylase, cellulases),

Forestry

Bacteria (e.g. Anaplasma phagocytophilum, Borrelia burgdorferi, Coxiella burnetii), viruses (e.g. hantavirus, tick-borne encephalitis virus,) parasites (e.g. Toxoplasma gondii).

Metal processing (where metal working fluids applied)

Bacteria (Pseudomonas spp, Mycobacterium immunogenum), mould/yeasts (e.g. Fusarium spp), endotoxins.

Wood processing

Bacteria (mainly gram-negative but also Actinomycetes), fungi (e.g. Aspergillus spp, Alrernaria spp­ and yeasts,), endotoxins

Waste collection, treatment and sorting

Fungi (e.g. Aspergillus fumigatus, and yeasts), infectious (e.g. Salmonella, ) and non-infectious bacteria (e.g. E. Coli, actinomycetes).

Endotoxins, glucans, and viruses (e.g. Hepatitis A, Hepatitis B)

Workplaces with air conditioning and high humidity (e.g. textile industry, print industry, and paper production)

Fungi (moulds and yeasts), bacteria (e.g. Legionella spp, Pseudomonas spp).

Endotoxins, and allergens

Archives, museums, libraries

Fungi (Aspergillus and yeasts), bacteria.

Endotoxins

Building and construction industry (material processing, building renovations)

Moulds, bacteria.

Endotoxins

Legislation

European legislation aims to minimise the health risks from biological agents in the workplace, principally through the provisions of Directive 2000/54/EC “on the on the protection of workers from risks related to exposure to biological agents at work”.[2] Measures proposed include containment categories for laboratory work and industrial processes.

It should be noted that, as consequence of the strict definition applied, the Directive does not explicitly address exposure to biological agents forming bioaerosols. However, the above criteria for risk classification, as well as the outlined principles of risk assessment, prevention and control described below, are generally applicable also to such agents.

The Directive lays down requirements for notification of selected activities to authorities. This includes a requirement to give at least 30 days prior notice to the competent authority of the use for the first time of biological agents in Groups 2, 3 or 4.

For workers likely to be exposed to certain biological agents, employers have to keep records including information about exposure and health surveillance. Workers have to be provided with access to their personal data.

As with other individual Directives under the EU OSH Framework Directive, the Biological Agents Directive includes requirements regarding the provision of information and training; and on the consultation with and participation of workers and/or their representatives in connection with matters covered by this Directive.

As well as general information and training regarding issues such as potential risks to health and precautions to be taken the Directive makes provision for workers to be given information in particular cases, including procedures to be followed in the case of a serious accident or incident involving the handling of a biological agent; and handling a group 4 biological agent.

As noted earlier, these regulations, including the classification mentioned previously, are minimum requirements and have been implemented into national legislation. As part of their national implementation of the provisions of the EU Directive some Member States have also introduced Codes of Practice and guidelines for safe handling of biological agents including selected sectors and occupations.

Occupational exposure limits

The essential difference between biological agents and other hazardous substances is their ability to reproduce in presence of favourable conditions. This ability, and the lack of documentation of agent-specific exposure-response relationships, complicates the establishment of effective exposure limits in workplaces and hence no occupational exposure limits are currently available for biological agents. However, it should be noted that some Member States have set limits for certain metabolites from such agents such as certain toxins.

For bioaerosols, several proposals for the establishment of exposure limits have been made by different organisations, particularly in relation to fungal and endotoxin exposures. However, these proposals were mainly developed for the assessment of indoor mould problems, or were frequently not health-based or performed outside a formal exposure standard setting process[11]. Exceptionally, the National Health Council of the Netherlands, in conjunction with the Nordic research council, have recently jointly proposed a health-based recommended exposure limit HBROEL of 90EU/m3 to be adapted by the industry (EU = Endotoxin Units – a measure of biologically active endotoxin)[12]. This proposal was based largely on studies of acute respiratory health effects. In the absence of adequate occupational exposure limits, the occupational exposure limits for exposure to organic dust established by some countries tend to commonly be used as guidelines for advising and protecting workers from exposure to biological agents in general (in the absence of specific data).

Risk assessment, prevention and control.

As noted above, Directive 2000/54/EC outlines the principles of risk assessment, prevention and control for biological agents[1]. In principle, employers are required to:

  • assess the risks posed by biological agents; and
  • reduce the risk to the workers by;
    • elimination or substitution;
    • exposure prevention and control;
  • inform and train workers; and
  • provide health surveillance as appropriate.

Strategies for the assessment and management of risks posed by biological agents may be affected by the nature of the process and activity involved. In general, where the work activity involves the intentional use of biological agents, such as cultivating a microorganism in a microbiological laboratory or using it in health care or food production, the biological agent will be known. This allows exposure to be monitored more easily and prevention measures can be tailored to the risk posed by the organism.

In contrast, when the occurrence of the biological agents is unintentional (that is occurring as a consequence of the work), such as in agricultural activities, during waste management and handling, the assessment of risks that workers are exposed to will be more difficult. Nevertheless, for some of the activities involved, information on specific exposures and protection measures is available, whereas for others control is subject to the general principles of Occupational Hygiene.

Risk assessment for biological agents should be performed in a proactive manner and similar to the one applied for other agents. However, some situation may be complex and in such cases any risk assessment needs to be adapted to the particular biological risk concerned. It is important that, once an activity where workers may be exposed to biological agents is identified, information about the exposures is collected. If the use of biological agents is deliberate then information about the nature and effects of the biological agent used should be included in the inventory of hazardous substances. When risks from biological agents are analysed it is also important to account not only for the workers directly involved but also for those who might be indirectly affected such as cleaning personnel.

Any risk assessment should pay particular attention to any vulnerable workers such as young persons, pregnant workers and those known to be immune-compromised. The Young People Directive (Council Directive 94 33 EC)[13] requires Member States to prohibit the employment of young people for “work involving harmful exposure to agents which are toxic, carcinogenic, cause heritable damage, or harm to the unborn child or which in any other way chronically affect human health”. Directive 92 85 EEC, relating to pregnant workers as well as those who have recently given birth or are breastfeeding[14], makes specific provisions for work with agents in Groups 2, 3 and 4 and national legislation (or guidance where available) should be consulted.

Conducting risk assessments for biological agents

A general risk assessment approach that can be applied by most businesses can consist of the following steps:

  1. Identifying the hazards and the workers at risk.
  2. Evaluating and prioritise the identified risks in terms of importance. This can be achieved by ranking of the risks on the basis of their probability to cause harm and the severity of the expected outcome.
  3. Adapting the work process or substituting the agent(s) to eliminate risk, and where this is not possible
  4. Identifying appropriate control and preventive measures and deciding which of them to apply
  5. Applying the identified preventive and control measures
  6. Recording findings and reviewing

It is important that risk assessments are regularly reviewed and revised where necessary. This includes whenever there are significant changes in materials, equipment, work methods, location or people involved and if there are accidents or complaints associated with the work.

Managing and reducing risks from biological agents

Following identification and analysis of risks, adequate methods of exposure prevention and control should be designed and implemented. Whenever possible, priority towards complete risk removal should be given, either by elimination of the process concerned or by substitution of the involved agents by others which are less hazardous.

If the exposure is not avoidable, it should be kept to a minimum by limiting the number of exposed workers (e.g by restricting access to relevant areas) and restricting the exposure time. The control measures must be tailored to the working process with preference given to those of an engineering and organisational nature. If needed personal protective equipment, for example laboratory coats or specific work clothing, gloves, and respirators may also be used whenever deemed necessary. Workers must be well-trained to follow safe working practices.

As noted above, the steps needed to remove or reduce the risks to workers will depend upon the particular biohazard, but there are a number of common actions that can be applied:

  • Many biological agents are communicated via air, such as exhaled bacteria or toxins of mouldy grain. For those it is important to avoid the formation of aerosols and dusts, including when cleaning or during maintenance.
  • Good housekeeping, hygienic working procedures and use of relevant warning signs are key elements of safe and healthy working conditions, for example special handwashing procedures and equipment such as non-contact fittings and colour coding of hospital waste. This includes workers not drinking, eating and smoking in working areas where biological agents may be present or handled.
  • Many microorganisms have developed mechanisms to survive or resist heat, dehydration or radiation, for example by producing spores. Decontamination measures for waste, equipment and clothing and appropriate hygienic measures for workers should be included, for example decontamination areas with showers for changing work clothes in waste management. Instructions for safe disposal of waste, emergency procedures, and first aid should also be made available.

In some cases preventive measures can include vaccination to be provided to workers on a voluntary basis (where an effective vaccine exists – for example for hepatitis B – although this should not be relied on as the sole protective measure).

An outline of preventive measures relevant for workplace hazards posed by biological agents in specific occupations is provided in Table 2.

Table 2. Examples of potential hazards involving biological agents across different occupations and relevant measures that may be used to control/prevent exposure

Occupations at risk

Hazards/Risks

Preventive measures

Food (cheese, yoghurt, salami) or food additive production, bakeries

Moulds/yeasts, bacteria and mites cause allergies.

Organic dusts of grain, milk powder or flour contaminated with biological agents

Toxins such as botulinus toxins or aflatoxins

Closed processes

Avoid aerosol formation

Separate contaminated work areas

Appropriate hygiene measures

Health care

Several viral and bacterial infections such as HIV, MRSA, hepatitis, or tuberculosis

Needlestick injuries

Safe handling of infectious specimens, sharps waste, contaminated linen and other material, separate collection and colour coding of waste.

Safe handling and cleaning of blood spills and other body fluids

Adequate protective equipment, such as gloves, clothing, glasses, etc.

Appropriate hygienic measures

Laboratories

Infections and allergies when handling microorganisms and

cell cultures, e.g. of human tissues

Accidental spills and needlestick injuries

Microbiological safety cabinets.

Dust and aerosol–reducing measures

Safe handling and transport of samples

Appropriate personal protection and hygiene measures

Decontamination and emergency measures for spills

Restricted access

Biosafety label

Agriculture

Forestry Horticulture

Animal food and fodder production

Bacteria, fungi and their integral constituents (i.e. endotoxins and glucans), mites and viruses transmitted from the animals, parasites and ticks.

Respiratory problems due to microorganisms and mites in organic dusts of grain, milk powder, flour, spices

Specific allergic diseases like farmer's lung and bird breeder's lung

Dust and aerosol-reducing measures.

Avoiding contact with contaminated animals or equipment

Protection against animal bites and stings

Preservatives for fodder

Appropriate cleaning and maintenance procedures

Good housekeeping

Metal processing industry Wood processing industry

Skin problems due to bacteria and bronchial asthma due to moulds/yeasts in circulating fluids in industrial processes such as grinding, pulp factories and metal and stone cutting fluids

Local exhaust ventilation.

Regular maintenance, filtering and decontamination of fluids and machinery

Skin protection

Appropriate hygiene measures

Working areas with air conditioning systems and high humidity (e.g. textile industry, print industry and paper production)

Allergies and respiratory disorders due to moulds/yeasts

Legionella

Dust- and aerosol-reducing measures

Regular maintenance of ventilation, machinery and work areas.

Restrict number of workers

Maintaining high hot (tap) water temperatures

Archives, museums, libraries

Moulds/yeasts and bacteria cause allergies and respiratory disorders

Dust and aerosol reduction

Decontamination

Adequate personal protective equipment

Building and construction industry, processing of natural materials like clay, straw, reed; redevelopment of buildings.

Moulds and bacteria due to deterioration of building materials

Dust and aerosol reducing measures

Appropriate personal protection and hygiene measures

Use of checklists

Checklists can be very useful in the process of risk assessment. EU-OSHA has previously developed a checklist that can be used as a model for the identification of workplace hazards and potential prevention measures sourcing from biological agents. Depending on the activity involved a more-in depth assessment may be required in case hazards from biological agents are required. The list is available as part of a factsheet on risk assessment[15].

Health and safety during treatment, sorting and disposal of waste

During the last decades there has been in increase in risks of biological agents concerning workers performing activities related to waste sorting and treatment, mainly as a result of environmental policies towards reduction of waste and pollution, a massive increase in volumes of materials handled, and the implementation of new technologies.

Waste handling and treatment activities are generally diverse in nature and may occur in several different sectors. These may include recycling plants for paper, glass, synthetic and wrapping materials, composting plants, landfills, sewage plants and health care facilities. Evidently the activities and materials involved can also be diverse, resulting in a complex exposure situation of multiple biological agents including infectious pathogens as well as non-infectious bioaerosols such as fungi, bacteria, mycotoxins, endotoxins and glucans. The composition of microorganisms may vary over time either as a result of agent multiplication or due to the activity involved. For example, workers in landfill sites may potentially be exposed to increased levels of bioaerosols during the dumping of waste whereas, during sorting activities of recycled materials, the exposures may vary depending on the exact composition of the handled waste.

As exposures and health outcomes may be different between sectors it is rather important that preventive measures are tailored for the sector and activity involved. In such activities complete elimination of the exposure and associated risks seems rather unlikely and therefore focus has been given towards prevention measures aiming at a reduction of the generation of dust and bioaerosols in the workplace. In this line several Member States have developed preventive measures including the reduction of hand sorting by the introduction of mechanical means, use of sorting cabins with proper ventilation, local exhaust ventilation, closed vehicles equipped with air filters and the use of adequate protective clothing. Hygiene plans, regular cleaning and decontamination measures can also contribute to a considerable reduction in exposure of workers. A hierarchical summary of identified preventive and control measures relevant for the waste industry is provided in a review performed by The European Agency for Safety and Health at Work[16].

(This article is based in part on EU-OSHA Factsheet 41: Biological agents)

(NB: This Introductory article replaces the original text which can be found as the article 'Bioaerosols and OSH')


Links for further reading

EU-OSHA - European Agency for Safety and Health at Work (2010) E-fact 53: Risk assessment for biological agents. Available at https://osha.europa.eu/en/tools-and-publications/publications/e-facts/efact53/view

EU-OSHA - European Agency for Safety and Health at Work (2009) Biological agents and pandemics: review of the literature and national policies. Available at https://osha.europa.eu/en/tools-and-publications/publications/literature_reviews/lit_review_biological-agents/view

Kolk A. Managing biological hazards in the workplace. In Magazine 6: Dangerous Substances Handle with care. Bilbao, Spain. EU-OSHA – European Agency for Safety and Health at Work 2003. 31-36. Available at https://osha.europa.eu/en/tools-and-publications/publications/magazine/6/view

UK HSE – biological agents: http://www.hse.gov.uk/biosafety/information.htm

World Health organisation: http://www.who.int/en/

US OSHA - biological agents: https://www.osha.gov/SLTC/biologicalagents/

References:

  1. 1.0 1.1 European Union (2000) Directive 2000/54/EC of the European Parliament and of the Council of 18 September 2000 on the protection of workers from risks related to exposure to biological agents at work. Off J Eur Communities L 262/21:21–45.
  2. S.I. No. 572 of 2013 Safety, Health And Welfare at Work (Biological Agents) Regulations 2013
  3. Biological Agents Ordinance (Verordnung über Sicherheit und Gesundheitsschutz bei Tätigkeiten mit Biologischen Arbeitsstoffen), Biostoffverordnung (BioStoffV)
  4. Control of Substances Hazardous to Health Regulations 2002
  5. GESTIS Biological Agents Database Hazardous substance information system of the German Social Accident Insurance. Available at: http://www.dguv.de/ifa/gestis/gestis-biostoffdatenbank/index-2.jsp
  6. INRS Baobab - BAse d'OBservation des Agents Biologiques. Available at: http://www.inrs.fr/publications/bdd/baobab.html
  7. Dutkiewicz J, Cisak E, Sroka J, et al (2011) Biological agents as occupational hazards - selected issues. Ann Agric Env Med 18: 286–293.
  8. IARC (1994) Volume 61 Schistosomes, Liver Flukes and Helicobacter Pylori. International Agency for Research on Cancer, Lyon, France
  9. IARC (2012) Volume 100C: Arsenic, Metals, Fibres and Dusts. International Agency for Research on Cancer, Lyon, France
  10. IARC (2012) Volume 100B: Biological Agents. International Agency for Research on Cancer, Lyon, France
  11. Eduard W, Heederik D, Duchaine C, Green BJ (2012) Bioaerosol exposure assessment in the workplace: the past, present and recent advances. J Env Monit 14:334–339. doi: 10.1039/c2em10717a
  12. DECOS (2010) Endotoxins: health based recommended exposure limit. A report of the Health Council of the Netherlands, publication no. 2010/04OSH. Health Council of the Netherlands, The Hague
  13. Directive 94/33/EC on the protection of young people at work http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=LEGISSUM:c11205
  14. Council Directive 92/85/EEC of 19 October 1992 on the introduction of measures to encourage improvements in the safety and health at work of pregnant workers and workers who have recently given birth or are breastfeeding. http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex%3A31992L0085
  15. E-fact 53: Risk assessment for biological agents https://osha.europa.eu/en/publications/e-facts/efact53/view
  16. Brun E (2007) Expert forecast on Emerging Biological Risks related to Occupational Safety and Health. European Agency for Safety and Health at Work, Bilbao, Spain
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