If a poor community believes it is being poisoned, how can it find out if its fears are justified? Grant Clark visits South Durban, where outdated government legislation has left locals fighting their own battle for the truth.
At first glance, the plastic buckets stacked in the corner of the environmental NGO office look like any others.
But the containers are an unlikely weapon in one poor community's fight against oil companies they say are responsible for widespread ill-health caused by years of pollution.
The vessels are used by a network of local volunteers, known as the Bucket Brigade, to gather air samples in neighbourhoods bordering oil refineries, as part of a campaign to monitor and document air pollution which they believe is coming from the plants.
In South Africa, as in many developing and newly industrialised countries, legislation on air pollution has failed to keep pace with mushrooming industries.
So local residents, like many in poor communities around the globe, have faced the problem of investigating their claim that industries on their doorsteps are making them sick.
The small yet tenacious South Durban Community Environmental Alliance (SDCEA) has become the first African grassroots group to take the science into their own hands by taking their own air samples.
An internationally celebrated example of environmental justice in action, the campaign has seen a once-despondent community play a major part in lobbying the petroleum giants to change the way they process fuel.
The bucket air sampler has been a key weapon in the campaign
Durban, a port city on South Africa's east coast, is home to almost three million people.
More than 280,000 of them live in south Durban, crammed into an industrial basin which houses the country's largest petrochemical hub as well as dozens of other chemical and manufacturing plants.
The low-income suburbs of Merebank and Wentworth, inhabited by people of mainly Indian and mixed-race descent, are literally surrounded by two large oil refineries and a paper mill.
The residents were settled there in the 1960s, several years after the petroleum plants were built, under apartheid segregation laws as a source of cheap labour for the industries.
The refineries are operated by Engen, a South African and Malaysian-owned company, and Sapref, a joint venture by British multinationals Shell and BP.
The SDCEA was founded in 1993, and carried out an initial informal survey of the community.
The group says this revealed a high incidence of cancer and respiratory ailments among residents.
Benzene, a compound produced during the oil processing process, is a known cancer-causing agent while sulphur dioxide (SOČ), another major refinery by-product derived from burning oil, is a respiratory irritant and has been shown to aggravate asthma.
The south Durban industrial basin is home to 280,000 people
Believing the refineries were to blame, the Danish-funded NGO began mobilising people to take action against the oil corporations.
With many locals employed at the plants, residents were initially fearful about protesting.
"Some didn't even want to talk to us," says chairman Desmond D'Sa, a former petroleum plant worker who lives near the Engen installation.
But, inspired by a personal endorsement of their struggle by then president Nelson Mandela in the mid-to-late 1990s, hundreds now turn out for regular anti-pollution demonstrations.
A decade ago, the oil companies had few dealings with their residential neighbours and the relationship was poor.
Now both refineries have liaison committees where representatives from both sides meet to thrash out environmental concerns.
"If you look at it historically, there's no question this area has a pollution problem," says Wayne Hartmann, Engen refinery managing director.
"Are we part of that problem, historically? Yes, we use a lot of fuel and we have SO2 emissions," he says.
Former refinery worker Desmond D'Sa now leads the campaign
But over the past 10 years, he says, the plant has reduced its emissions from an average of 46 tonnes a day in 1998 to a daily 25 tonnes this year.
Mr Hartmann admits, though, that the refinery still occasionally exceeds the stipulated guidelines for the maximum of SO2 which can be emitted in a 10-minute peak period.
Sapref says it has spent more than $40m over the last 11 years on enhancing its environmental performance.
"We've fitted low nitrogen oxide burners on all furnaces to reduce our emissions," said spokesperson Phumi Nhlapo.
"We've also switched from firing up their production processes with heavy fuel oil to gas, to reduce smoke and SO2 emissions," he said.
A new sulphur recovery unit has reduced SO2 emissions by 46%, the company says.
These changes are thanks, in no small part, to the south Durban communities' most successful weapon - the bucket air sampler.
It uses a small vacuum pump to suck air into a specialised clear plastic bag inside the bucket.
A laboratory in the US analyses samples and returns results detailing detected toxic gases such as sulphur dioxide, nitrous oxides and benzene.
Residents settled in the 1960s, several years after the petroleum plants were built
The data has then been used to lobby Engen and Sapref.
"We think they have a usefulness, as long as the samples are captured, handled and transported properly. In fact, we use similar containers for monitoring at the plant," said Engen's Mr Hartmann.
But, he said, air pollution levels can fluctuate fast and the samplers do not record a pattern over time.
Despite recent improvements, however, the health problems are still there.
A 2002 medical study, carried out by Durban's Nelson Mandela School of Medicine and a US university, found that an abnormally high 52% of students and teachers at a primary school bordering the Engen plant suffered from asthma.
It found that increases in air pollution tended to aggravate asthma symptoms in children.
The Durban basin houses the country's largest petrochemical hub
The petrol producers do not dispute the findings but argue that researchers were unable to establish a causal link between air pollution and the high prevalence of asthma among the school population.
For the community, the next step is to take legal action.
But, according to internationally recognised environmentalist Bobby Peek, targeting the companies would be difficult as it would be near-impossible to prove that illnesses suffered were caused by pollution coming from a particular plant.
Mr Peek, who grew up beneath Engen's stacks, says the activists are now considering taking action against the authorities.
"We are now looking at suing the government on constitutional grounds, for failing to ensure our right to protection from a harmful environment as stipulated in the constitution," he said.
A new batch of environmental laws, the National Air Quality Management Act, has just been passed by the South African parliament to replace outdated 1965 legislation with tighter controls and tougher sanctions.
But it will be two years before the full framework to enforce these is in place, Mr Peek said.
Martinus van Schalkwyk, the minister of environmental affairs and tourism, visited the south Durban basin earlier this year and said there were measures in place to improve the situation.
"I share the anger and frustration of this community. It is long overdue," he told the South African Broadcasting Corporation.
The local authorities have also established a "Multi-Point Plan" for the area. They say is a powerful model for tackling pollution and point to a 40% reduction in sulphur dioxide emissions in recent years.