The journey to a greener pathology laboratory

In 2021 the British Society of Veterinary Pathologists delegated a new single task BSVP Green Team to focus on challenges surrounding sustainability in veterinary pathology and to explore how the vet path community might work together. It is envisaged that the work of this group may include (but will not be limited to!) the development of a webpage resource on sustainability in our profession, sharing experiences, promoting good practice, and fostering links with other green groups within the profession (e.g. Vet Sustain).

The BSVP Green Team draws members from across the profession including veterinary pathologists in commercial diagnostic laboratories, universities, toxicological research and veterinary pathology residents in training. There is a lot of information ‘out there’ on sustainability, but navigating this material to find practical, feasible suggestions for change within the UK veterinary pathology context is our goal.

Historically, the first response to raising the spectre of sustainability in the pathology setting is ‘we can’t do anything about the chemicals’, shutting down all further conversation. However, as we all know, the sustainability footprint of any business involves so much more than just ‘the chemicals’. Thanks to leadership shown by the NHS, the Royal Colleges and groups such as Vet Sustain, many laboratories already have programmes in place to address general issues such as waste and energy.

Readers of these blogs will be very aware of Investors in the Environment, but other frameworks for laboratories pursuing sustainability here in the UK include, LEAN (Laboratory Efficiency Action Network) coordinated from Bristol University, and LEAF (Laboratory Efficiency Assessment Framework) run by University College London.

Still, one must ask - What about those chemicals?! There is no doubt this is a biggie and it is receiving a lot of attention. The two biggest on the block are probably formaldehyde and xylene.

Formaldehyde is classified by WHO as a Group I carcinogen, short term exposure may cause eye, nose and throat irritation and long term exposure may induce dermatitis or may trigger IgE-mediated nasal allergy in atopic people. Formaldehyde biodegrades readily in air, water and soil under both aerobic and anaerobic conditions. In the air, formaldehyde breaks down in sunlight to form carbon monoxide and formic acids, components of acid rain. Formaldehyde is not bioaccumulative and does not persist in the environment, but its continuous release and formation result in long-term exposure near sources of release.

The toxic effects of xylene are variable depending on time and degree of exposure. At high exposure it may produce pulmonary oedema and hepatotoxicity. It is highly lipid soluble and can produce central nervous system depression, with signs varying from headaches, through to loss of balance, weakness or speech impairment with chronic exposure. Xylene evaporates quickly, meaning that most xylene that gets into soil or water is released into the air and broken down by sunlight and less harmful chemicals within a couple of days. However, in underground water, it may take several months for xylene to degrade.

Formalin (formaldehyde in solution) has served as the routine tissue fixative for over 100 years, with the search for a safer alternative having almost as long a history. So what is the problem? Laboratory protocols and work flows are optimised for the use of formalin-fixed paraffin-embedded material. Pathologists are conversant with the artifacts created by formalin fixed tissue, and may use them in decision making. The artifacts of alternative fixatives are slightly different which may not be a problem in most cases, but may cause uncertainty in borderline situations. It is uncertain if long-term storage of tissue in alternative fixatives would yield satisfactory tissue preservation. Formalin is not an ideal fixative, given its effects on nucleic acid degradation and ability to introduce artificial mutations. Nevertheless, the protocols in place have worked with these problems and are validated and established.

A number of formalin substitutes have been proposed including honey and other natural sweeteners, but the front runners are ethanol-based solutions. Vacuum packaging of samples (to minimise the volume of formalin used) is another method which has been trialled in one large medical pathology service in Wales. No alternative fixative has so far gained wide acceptance. One of the aims of BSVP’s Green Team is to promote exploration of possible alternatives in this arena.

Xylene is used as a clearing agent in routine histological tissue processing and staining, and like formalin there has been much investigation into alternatives. Alternative processing procedures are established and here it seems to be convention and human behaviour which has been the sticking point. Michigan State University Veterinary Diagnostic Laboratory has made this change. We applaud their success and are very grateful to Professor Matti Kiupel for allowing us to share his method of xylene free processing. He comments:

“I am actually quite proud of us having gone this way, and many of our pathologists here didn’t even notice when we changed, or still don’t know that we are xylene free, and even now most people at the university are unaware of it, or really never paid attention to it. The person that ran the recycling unit at the university made it a big deal with upper administration that they cut the xylene waste by 80%”.

And this is the main aim of the BSVP pages on sustainability in veterinary pathology: sharing ideas and examples of what works to encourage and give courage to people desiring change. The pages are now live and open to all. Please visit to find out more about the green veterinary pathology laboratory.