Wake up call

02 October 2014

Jak Fazakerley, environmental consultant at Crestwood Environmental, discusses the health hazards and risks associated with occupational exposure to bioaerosols.

Industry experts warn that organic waste companies need to be more aware of, and act upon, the potential occupational health risks associated with bioaerosols, particularly in the absence of specific legislation and guidance on the hazard. A failure to ensure all necessary health and safety precaution measures are implemented on site could substitute neglect, and thus warrant further investigation from the HSE and insurance companies.

The term bioaerosol is used to describe airborne micro-organisms (i.e. bacteria, fungi or viruses) or their products (i.e. enzymes, endotoxins or glucans) that originate from organic matter, animals and humans. Typically, consisting of very fine particles measuring less than 20 microns in diameter, bioaerosols are omnipresent and variable in time, composition and concentration. 

A variety of new industrial activities have emerged in recent years in which exposure to biological agents can be prevalent. Very often staff connected to organic waste transfer stations and waste treatment sites are continuously exposed to the conditions which excel the formation of bioaerosols, including loading and unloading, shredding, turning and screening, as well as complex diurnal meteorological variations and the poor design of production and storage systems. The degree of process control employed during these operations varies depending on the size and location of the site, the nature of the feedstock and the intended use of the end product.

Health effects of bioaerosols
Despite the benefits of organic waste management, there are concerns that occupational exposure to bioaerosols could be detrimental to health. Both the ingestion and inhalation of bioaerosols can lead to headaches, nausea, fatigue, respiratory diseases (i.e. farmer’s lung, mushroom workers lung, asthma and chronic bronchitis), gastrointestinal illness, eye irritation, dermatitis, acute toxic effects and even cancer. Individuals with severely compromised or suppressed immune systems, e.g. following an organ transplant or if suffering from immune deficiency diseases, are at particular risk.

There are no occupational exposure limits (OELs) for biological agents, and for most of them, no dose-response relationship can be determined due to the number of bioaerosols and the complexities associated with human responses to different micro-organisms. Furthermore, cumulative exposure conditions may exist at workplaces. 

Mitigation to occupational bioaerosol exposure 
The Health and Safety Executive (HSE) document ‘Health and Hazardous Substances in Waste and Recycling, Waste 27’ (2012) and The Control of Substances Hazardous to Health Regulations (COSHH Regulations 2002) requires organisations to assess the risk from harmful substances and prevent or control exposure to them.
This means that employers, such as local authorities, should follow the hierarchy of prevention, containment and protection measures so that workers’ exposure is adequately controlled so far as reasonably practicable.

Very often, the mitigation measures implemented to reduce occupational exposure to bioaerosols are based on a risk assessment which identifies the hazard, assesses exposure, estimates the risk and characterises the risk so to establish the baseline. The scope, level of detail and focus will be site-specific due to temporal and spatial scales.
Measures range from information dissemination, engineering controls and good working practises, including: 
  • Providing induction and refresher training so to adopt a good approach and attitude to health and safety
  • Establish risk zone working practices
  • Provide adequate PPE
  • Ensure vehicle cabs are closed and have appropriate measures to encourage drivers to keep the windows closed
  • Provide adequate welfare facilities
  • Checks to ensure collection crews adopt good hygiene practices
  • Implement health screening and monitoring to identify respiratory illness or sensitiveness.
Occupational bioaerosol monitoring
A range of monitoring equipment is available to measure occupational exposure to airborne biological agents, including the Casella, IOM Samplers and CIP 10-M (ARELCO). This sampler, for example, is autonomous with a battery life of around 10 hours, therefore covering typical shift duration. Because it is designed not to impact on the worker’s activity it provides a true representation of the amount of bioaerosol present around the breathing zone of the worker. It works by collecting biological particles in 2ml of liquid medium inside a rotating cup (made of sterilisable material) fitted with radial vanes to maintain an air flow rate of 10L/min−1 at a rotational speed of approximately 7000 rpm. The sampled particles follow a helicoidal trajectory as they are pushed to the surface of the liquid by centrifugal force, which creates a thin vertical liquid layer. Once they are collected, they are plated on agar medium at different dilutions, incubated and counted. They can then be used for further analysis such as endotoxins or glucans.