DEEP in the laboratory's inner core, a never-ending cycle of fish exist in stark compact tanks.

Exotic tiny striped zebrafish and silvery fathead minnows are

part of the unrelenting march forward of a global chemical industry, in the bid to produce medicines, industrial chemicals and pesticides which do not harm the natural environment.

When they have outlived their use the fish are terminated and work begins on a new batch.

Fish testing at Astra Zeneca is not about finding medicinal cures, but about their possibly poisonous effects on the earth's fragile ecosystem.

Astra Zeneca's state-of-the-art lab could be classed as the official watchdog for the chemical industry.

It is a global leader in assessing the potential impact of chemical substances on the environment.

Animal testing, and that includes fish, is a highly regulated industry and Nigel and his staff must comply to animal welfare rules.

He explained: "All testing of animals in the UK is overseen by the Home Office and fish are no different.

"They are vertebrate animals, they have a backbone, so are included in the legislation, and the work we do is regulated in the same way.

"We have frequent unannounced visits from the Home Office to ensure we are treating the animals properly and adhering to legislation.

"An external vet also checks on the welfare of the fish and we have an animal ethics committee consisting of lay people and people from within the lab."

The Brixham laboratory began life in 1948 as a marine research station for ICI Paints.

Environmental science began to dominate the lab's function throughout the 60s and 70s and by 1986 major expansion was needed to cope with an increasing workload as the lab's reputation for excellence became world renowned. Each year, scientists at the lab research chemicals in a myriad of ways, including testing thousands of fish, to find out if and how they effect plants, invertebrate animals and fish and the wider environment.

Their research is split 50/50 between work for Astra Zeneca and other companies throughout the world.

Developing a new drug takes between seven to 11 years, and the Brixham lab is involved in the later part of the process.

In 1993, following the de-merger of ICI, the lab transferred to Zeneca's ownership and in 1999 became part of the Astra Zeneca organisation, an Anglo/Swedish company with its headquarters in London.

"It's a massive company. We are a very small part of it," Nigel said.

He joined Astra Zeneca in 1980, becoming site manager in Brixham in January 2008.

Before joining Astra Zeneca, he worked at Plymouth's Drake's Island Adventure Centre as head of marine biology.

In 2008 the Brixham lab underwent a £13million refurbishment and expansion, opened by Princess Anne.

Today it employs 90 full-time staff, the majority of whom have degrees, including microbiologists, ecologists, oceanographers, marine biologists, hydrogeologists, mathematicians, biologists, statisticians, chemists, chemical engineers, biochemists and information specialists.

Half of the staff are women. When Nigel joined the company in 1980, he said there were 56 staff and only three were women.

"It's a sign of the change and a sign the company is very supportive of staff, and people taking their maternity leave.

"We have very flexible working arrangements here, we are lifestyle friendly.

"Between 50 and 60 of the staff live in Brixham so we are contributing to the economy from that sense.

"It's the sort of employment that Torbay generally, let alone Brixham, needs because it's relatively well paid, permanent employment."

Nigel says Astra Zeneca constantly strives towards the three 'Rs' — Reduce, Refine and Replace.

This means to reduce the amount of animals it tests, to refine the work in terms of creating less impact on the animals and where possible replacing animal testing with something else.

The lab also seeks to ensure the fish in its care live a comfortable and fulfilling life.

Gareth Readman, head of fish husbandry, said: "It's not quite as simple as putting plastic fronds in the tank and thinking the fish are more fulfilled with that.

"We measure levels of stress in fish through levels of hormones and actually testing what makes a fish's life better, not just putting our human perception on what makes their life better.

"We stimulate the wild environment by using lighting and types of feeding.

"The lighting doesn't go from daylight to night instantly, but goes through a dusk period."

Astra Zeneca recently splashed out £4.1million on a new innovative fish husbandry centre, where zebrafish and fathead minnows are bred for research.

Surprisingly, the genetic structure of zebrafish has more in common with humans than the genetic structure of rats, Nigel said.

"Their genetic structure is very well understood and easy to culture," he added.

"They are easy to manipulate and their behaviour is well understood."

Because of their robustness, fathead minnows from the USA are also used for research purposes, along with rainbow trout and daphnia, a species of water flea found in Europe.

As the female water flea reproduces asexually, each offspring is genetically the same, removing genetics from the equation, Nigel said.

Sometimes, the lab uses young zebrafish to ascertain the safety of new medication early on in its development.

Scientists compare the movement of fish which have been exposed to a certain chemical to fish which haven't.

If the chemical causes the fish to suffer a seizure its movements will become more rapid.

"It's a simple means of actually finding out if a medicine might have that effect very early on before you test it on animals such as rats and dogs, which is done elsewhere in the company," Nigel said.

"Fish are exposed to a chemical for a period of time. We measure how much chemical is in the fish until it reaches a plateau — and can take no more of the chemical.

"Then we test how fast the chemical comes out when you stop giving them the chemical.

"We want to find out if the chemical passes up the food chain, like another DDT (the first synthetic pesticide of the modern age which ultimately created widespread concern as an environmental hazard) which went to birds."

The second key area of research at Astra Zeneca involves chemistry and aims to understand the processes leading to the breakdown and removal of pharmaceutical residues in sewage treatment plants and the wider environment.

Nigel said: "We are trying to find out what happens to chemicals when they go into the environment, about how they will break down and change, whether it will accumulate and if so what the effects might be.

"Most substances will break down and become harmless but we have to understand what the impact in the environment might be."

The chemical laboratories, where scientists simulate river, ground and sewage treatment works, sit behind the offices in Astra Zeneca's new building.

"We combine water and mud with chemicals for about 100 days," Nigel said.

"Bottles are taken quite frequently during the test to see how the chemical has changed. It is the first phase in a risk assessment."

Ambassador's from the company regularly visit local schools to encourage youngsters to be inspired by science and the lab provides work experience for students.

Nigel said the company has also funded an advisor from Tomorrow's People a charity that helps the unemployed get back into work for the last 10 years by paying the advisor's wages and providing an office.

It is also a partner to specialist science schools in Kingsbridge and Kingsteignton, Paignton Zoo, Living Coasts and Torbay Coast and Countryside Trust.

"We do quite a lot to support local causes," Nigel said. "We are focusing on two areas at the moment: healthcare and science education.

"Our focus is the transition from primary to secondary school.

"It's about encouraging and inspiring, we want people to think about career opportunities in science."