Last reviewed 20 February 2013

Mike Everley examines the precautions companies should take to prevent employees being exposed to hazardous biological agents.


A Health Protection Agency (HPA) employee was exposed to the risk of infection from E.coli while transferring bacteria from a laboratory to a discard area at the HPA’s Centre for Infection in north London.

The bacteria were contained inside metal bins that were then placed inside a transfer trolley. However, as the employee lifted one of the bins, his hand slipped and the unit’s lid opened, allowing more than 100ml of the bacteria to spill onto the floor. Two other employees in the area were also exposed. Fortunately though, no one subsequently became infected. The HPA pleaded guilty to breaching section 2(1) of the Health and Safety at Work, etc Act 1974 (HSWA).

Biological agents and E.coli

Biological agents can mainly be categorised as belonging to one of the following five groups: Bacteria, (E.coli is a bacterial infection), Rickettsiae and Chlamydia, Viruses, Fungi and Protozoa.

Depending upon their nature, biological agents can be categorised under the following Hazard Groups.

  • Group 1 — unlikely to cause human disease.

  • Group 2 — can cause human disease and may be a hazard to employees. Unlikely to spread to the community and there is usually effective prophylaxis or treatment available.

  • Group 3 — can cause severe human disease and may be a serious hazard to employees. It may spread to the community and there is usually effective prophylaxis or treatment available.

  • Group 4 — causes severe human disease and is a serious hazard to employees. It is likely to spread to the community and there is usually no effective prophylaxis or treatment available.

E.coli 0157, full name Escherichia coli 0157, is a bacterium that lives in the gut of animals, including cattle, sheep, deer and goats. Simply carrying the bacterium will not normally cause an animal any harm or illness, but if contacted by humans, the toxins it produces can cause illness ranging from diarrhoea to kidney failure. In some case the illness can be fatal, with young children and the elderly at the greatest risk.

E.coli 0157 is unusual in that very few individual organisms are needed to infect humans. People can become infected through a number of routes including the consumption of contaminated foods, direct contact with animals, contact with animal faeces and person-to-person spread both in families and institutions.

According to the health and safety specialist inspector involved in this particular case: “E.coli 0157 is a highly infectious and potentially deadly bacterium, and there are well-established practices for handling this safely. But, in this case, these practices were not met, exposing several staff, and potentially their families, to a real risk of infection”.

Statutory requirements

The prosecution was taken under section 2(1) of the HSWA which requires that an employer ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his or her employees.

Although not used in this particular case, the Control of Substances Hazardous to Health Regulations 2002 (as amended) (COSHH) applies to biological agents where either there is the risk of exposure from a deliberate intention to work with them or where there is a risk of exposure arising out of a work activity but incidental to it. In the main, COSHH requires an employer to:

  • assess the risk to health created

  • where possible, prevent exposure or, where not possible, control exposure

  • ensure that the control measures are used, maintained, examined and tested

  • introduce effective emergency procedures

  • provide health surveillance and monitoring as necessary.

The main factors to consider in a biological agent assessment are:

  • the biological agents that may be present

  • what hazard groups they belong to

  • what form they are in (spores, cysts, etc)

  • the diseases they can cause

  • how and where they are present, and how they are transmitted

  • the likelihood of exposure and consequent disease (any susceptible workers)

  • whether it is possible to substitute them with a less hazardous agent

  • control measures and minimisation of numbers exposed o monitoring procedures and results

  • health surveillance results.

With regard to control measures, the following factors need to be considered.

  • As there are no strict safe exposure limits, exposure may have to be reduced to levels at the limit of detection — Limit Values and Benchmark Guidance Values, etc.

  • If exposure cannot be prevented, then it needs to be controlled.

  • The number exposed, or likely to be exposed, should be kept as low as possible.

  • Work processes and engineering controls should be designed to prevent or minimise the release of biological agents into the workplace.

  • The biohazard sign and other relevant warning signs should be displayed.

  • Plans should be drawn up to deal with accidents involving biological hazards.

  • Appropriate decontamination and disinfection procedures should be specified.

  • The means for the safe collection, storage and disposal of contaminated waste, after suitable treatment where necessary, including safe and identifiable containers, should be arranged.

  • The safe movement of biological agents within the workplace should be arranged.

  • Procedures for taking, handling and processing samples should be in place.

  • Collective protection, where possible, should be provided, or individual protection, in the form of personal protective equipment.

  • Vaccines, where they exist and for those not immune, should be provided.

  • Washing and toilet facilities should be provided.

  • Eating, drinking and the application of cosmetics in the workplace should be prohibited.


A subsequent investigation of the incident by the Health and Safety Executive (HSE) discovered that many of the bins had defects on the lid hinges that allowed them to fall open. Apparently, some of the equipment used in the process had been identified as being defective eighteen months prior to the incident, but no action had been taken to rectify this. In addition, employees were not issued with personal protective equipment, nor had they received adequate training in the standard operating procedure to follow when carrying out the transfer.

According to the HSE: “HPA should have developed and implemented a safe system of work for dealing with E.coli 0157 and for transferring and inactivating Hazard Group 3 waste. The equipment involved should have been well maintained and the employees provided with adequate training”.

The HPA was fined £25,000, with £20,166 costs, for exposing its employees to the risk of infection from the E.coli 0157 bacteria.

Lessons learned

In mitigation, the HPA claimed to have had no previous convictions and to have taken immediate remedial action. It had reviewed its method of work, retrained its employees and now carries out regular testing and maintenance on equipment. All of the bins were removed from service and repaired within seven days. In the longer term, the HPA carried out a thorough review of its health and safety management system with the intention of ensuring that a similar incident could not happen again.