Same Radionuclide. Same Therapy. Different Rules.

Over the past years, as Zereau has introduced its solutions for source-based filtration of radionuclides, anticipating on the expected growth of radionuclide therapies, we have learned an important lesson: managing radioactive wastewater is not only a technical challenge. It is also a regulatory and cultural one.

Yet cross a border, and the rules – and sometimes the underlying perception of risk – can change completely.

The radionuclide may be the same. The therapy may be the same. The administered activity may be comparable. Even the patient profile may be almost identical.

A few hours or several days?

One of the most visible differences is the required or accepted length of hospitalisation following radionuclide therapy.

For essentially the same treatment and dose, patients may remain in hospital for only a few hours in one country, while in another they may stay for one or several days.

This has an enormous impact on wastewater management. A patient discharged after several hours produces a very different wastewater profile inside the hospital from a patient staying for 24, 48 or 72 hours.

The technical challenge therefore does not start with the filter or the decay tank. It starts with understanding local clinical practice and the regulatory framework behind it.

What is an acceptable discharge?

The differences become even more interesting when we look at radioactive wastewater itself.

Some jurisdictions apply very low discharge limits. Others allow considerably more flexibility. In some countries, requirements can differ between hospitals, regions or between interpretations by local supervisory authorities.

And even the "type" of limit varies.

Is compliance based on:

the concentration of a radionuclide in wastewater? the total activity discharged over a certain period? a calculated exposure limit for members of the public? a combination of these?

All approaches aim to control radiological risk, but they can result in very different requirements for exactly the same hospital treatment of wastewater and solids.

There is another important question: where do you measure?

At the toilet? At the outlet of a dedicated treatment system? After mixing with other hospital wastewater? At the hospital sewer connection? Or somewhere further downstream? The location of the monitoring point can fundamentally affect how different wastewater management systems are assessed. This is particularly relevant where discharge limits are expressed as activity concentrations. Source-based solutions such as Zereau’s treat relatively small volumes of wastewater close to the source and therefore need to achieve very high radionuclide removal rates to meet a low concentration limit. Conventional decay tanks, by contrast, may collect much larger water flows, including toilet flushing water, shower water and other wastewater from the department that contains little or no radioactive contamination. This additional water dilutes the remaining activity before the concentration is measured.

As a result, comparing systems solely on the radionuclide concentration at the final discharge point may not provide a complete picture of their environmental performance. A system discharging a large volume of diluted wastewater may comply with the same concentration limit while releasing considerably more total radioactive activity than a source-based system discharging only a small volume of treated water.

“A sewer does not make radionuclides disappear. It simply moves them somewhere else.”

Liquid versus solid: another interesting difference

The regulatory treatment of solid radioactive waste adds another dimension.

From a technical perspective, capturing radionuclides in a small filter can be very attractive. Instead of storing hundreds or thousands of litres of contaminated water, the activity is concentrated in a compact, manageable solid waste stream that can be safely shielded, monitored and allowed to decay.

But regulations do not always favour this logic.

Some countries place strict limitations on the quantity of solid radioactive waste that may be stored or on how long it may remain on site. Other countries provide considerably more flexibility.

This can create an interesting regulatory trade-off between liquid and solid waste. Discharging activity through the sewer can sometimes be administratively easier than capturing that same activity in a controlled solid waste stream.

From an environmental perspective, that is at least worth reflecting on.

Same science, different perception of risk

Perhaps this is what continues to surprise us most.

We are talking about the same radionuclides, the same physical half-lives, comparable administered activities, similar patients and often the same pharmaceutical products.

The science does not change at the border. The regulatory interpretation does.

That is not necessarily a problem. Regulation develops from national legislation, infrastructure quality, water availability, clinical traditions, historical choices and different approaches to radiological protection. There does not have to be one universal solution.

But for an international company such as Zereau, it means that understanding local regulation is just as important as understanding filtration technology.

Our systems therefore cannot be designed around one single regulatory model.

They need to accommodate different frameworks:

hospitalisation periods discharge criteria monitoring points wastewater vs. solid-waste requirements

Fortunately, flexibility is exactly where source-based treatment has an advantage.

Innovation has to prove itself again – and again

There is another reality that comes with introducing a different approach. Innovation generally has to work harder to earn trust than established infrastructure. Even when it’s just logic. A conventional decay tank is familiar. It has been used for decades and is therefore easily understood, even when it requires considerable space, construction work and investment.

Source-based filtration is different.

Even when a solution has been successfully implemented in one country, this does not automatically constitute convincing evidence for a regulator or hospital in another. Sometimes it does not even create much additional confidence. The technology has to be explained, demonstrated and validated again within the local regulatory context.

As an innovator, we simply have to accept that. At Zereau, we continue to build that evidence country by country and hospital by hospital. We when it feels we’re showing things twice, three times, or…

Making growth possible

Ultimately, the discussion is bigger than whether one country prefers a concentration limit and another an total activity limit, or whether a patient stays for six hours or two days.

Nuclear medicine - and radioligand therapy in particular - is growing specatular and this seems only the begin. Hospitals need to be able to accommodate that growth without wastewater infrastructure becoming the limiting factor.

That requires solutions that are safe, environmentally responsible, scalable and economically attractive.

Traditional decay tanks will continue to have a role, and in some situations they remain a logical solution. But they require space and infrastructure and can become increasingly challenging when treatment volumes grow or when nuclear medicine needs to be introduced or expanded within existing hospital buildings.

Zereau’s source-based filtration perspective captures radionuclides close to where they are excreted, before they become diluted in large volumes of wastewater. Sometimes this can replace decay tank capacity. Sometimes it can complement existing tanks, providing extra capacity. And often source-based filtration is just the only solution to start with radionuclide therapies in a hospital.

That flexibility allows us to adapt to very different regulatory frameworks without losing sight of the actual objective: enabling hospitals to provide more treatments while managing radioactive wastewater safely, responsibly and efficiently.

Would it be easier if the rules were more consistent from one country to another?

Certainly.

But until then, we will continue doing what we have learned to do over the past years: understand the local rules, adapt the solution and keep moving forward.

“Same radionuclides. Different rules. Flexible solutions.”