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Occupational exposure


Are today’s best practices sufficiently robust to protect our workers?

Christine Clark
BSc MSc PhD FRPharmS

Participants at the ASHP Midyear meeting in December 2009 were privileged to hear a fascinating presentation from occupational health researchers-Melissa McDiarmid and Thomas Connor-concerning the occurrence of specific chromosomal abnormalities in healthcare staff who are exposed to cytotoxic agents (See page 15-16). Knowing that cytotoxic agents bind to cellular DNA and act like oncogenes, they hypothesised that similar chromosome changes to those seen in chemotherapy-induced secondary malignancies-myelodysplastic syndrome (MDS) and acute myelogenous leukaemia (AML)-would occur. They then used formal epidemiological methodology to look for these changes.

Chemotherapy-induced secondary malignancy has been well-researched and characteristic chromosome changes have been described in the literature. What McDiarmid and Connor have done is demonstrate that the signature lesions of therapy-induced MDS and AML occurred in a group of healthcare workers exposed to cytotoxics. They have also linked the changes to the level of exposure.

All of the sites involved in the study claimed to have implemented all the recommended safe handling practices. The researchers commented that where robust containment measures-in the form of a closed system transfer device-were routinely used spillages were eliminated and therefore exposure was reduced considerably.

What this elegant piece of research cannot tell us is what the threshold level of cytotoxic exposure for chromosomal changes is, whether there is a critical level of chromosomal changes required for the development of MDS or AML, or anything about what happens in European hospitals. Neither does it tell us about the relative risks of occupational exposure to cytotoxic drugs and other environmental carcinogens. However, what it does do is to reinforce the importance of adherence to robust procedures for containment and safe handling. It also underlines the need for validated procedures and equipment and a fundamental understanding of the risks. At the same conference several speakers pointed out that we have so far concentrated mainly on intravenous administration of cytotoxic agents although this is not the only route by which these products are administered. The National Institute for Occupational Safety and Health (NIOSH) is now investigating the use of intraperitoneal chemotherapy in operating theatres and the use of cytotoxic agents in veterinary oncology. One chief pharmacist emphasised the value of tracking a cytotoxic injection through the hospital to find out who handles it and what protection measures (if any) are used. He asked the audience how many of them had witnessed a thiotepa bladder irrigation, adding that it was a “very messy” procedure.

Eleven years ago when I described the early findings about the hazards of occupational exposure to cytotoxic drugs (Pharm J 1999;263:65-67) I was roundly chastised by some colleagues for raising the issue in a public arena. In the intervening years the topic has attracted more balanced comment, numerous safe handling guidelines have been published and many containment devices have been developed. These new findings, whilst hardly surprising, serve to deepen our understanding, confirm long-held suspicions and raise further questions. I hope that they will be received in the spirit of scientific enquiry and enlightenment that they deserve.

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