HENGDONG, China (REUTERS) - Scuffles broke out at the end of the first day of a landmark pollution trial in China on Friday as families who sued a chemical plant over high levels of lead in the blood of their children confronted lawyers representing the company.

Police had to shield one lawyer from angry families and their supporters as he left the courtroom in the town of Hengdong in central Hunan province following a sometimes heated hearing. Foreign media are usually barred from Chinese court sessions, but a Reuters reporter was allowed to attend.

Environmental lawyers say the trial is a test of Beijing's resolve to address the human cost of widespread pollution following decades of unbridled economic growth in China.

It is believed to be the first time a Chinese court has heard a case involving lead poisoning in a group of children. The trial also comes amid a series of public interest lawsuits filed since a revised environmental protection law that came into effect in January enabled the submission of such cases and increased the penalties for polluters.

Thirteen families from in and around the nearby town of Dapu have sought compensation from Melody Chemical, a chemical plant and metal smelter, over pollution that they say caused elevated levels of lead in the blood of their children and grandchildren.

Melody's lawyers told the court that most of the plaintiffs had no grounds to sue because it was impossible to prove they lived near the factory, adding the plant's emissions met the national standard.

Lawyers for the plaintiffs countered with evidence that the children lived near the plant, that tests showed there was lead in Melody's emissions and that the impact on the development of the children was clear.

When plaintiffs and their supporters converged at the front of the courtroom after the hearing, shouting at Melody's lawyers and the judges, one disabled plaintiff fell to the floor during a scuffle.

The court did not say when the trial would resume, although Hu Shaobo, a lawyer for the plaintiffs, said he expected a verdict within three months. Melody's lawyers declined to comment or identify themselves to Reuters.

"It's not fair," Ms Yang Yimei, the mother of two children with high lead levels, said after the hearing, wiping away tears.

"The expert said today that the effects of lead exposure will last their entire life. I don't know what to do."

In children, high lead exposure leads to cognitive delays and behavioural problems and can be fatal at extremely high levels. Its effects are permanent and irreversible.

Chewing pencils

Dapu's lead problem made headlines a year ago in an expose by state broadcaster CCTV, in which the head of the township was shown saying children might have raised their own lead levels by chewing on pencils.

After the broadcast, which said more than 300 children had high lead levels, officials opened an investigation and Melody was ordered to shut down.

Reuters reported last month that of the original 53 families who agreed to participate in the lawsuit, most dropped out, some because of pressure from local officials. Dapu authorities deny any interference.

Environmental law experts said the court's acceptance of the lawsuit was a sign of progress, since courts have usually refused to hear controversial pollution-related cases.

President Xi Jinping's recent focus on the rule of law had also sent a message to courts, lawyers said.

On June 1, China's supreme court issued a judicial interpretation which reiterated that even if emissions from polluting companies were within legal limits, they could still be liable for any harm caused.

"If courts begin to rule in favour of pollution victims more often in these types of cases, companies will be forced to internalise the cost of pollution," Mr Alex Wang, an expert in Chinese environmental law at the UCLA School of Law, told Reuters before the trial.

"Local governments faced with depressed economic conditions will likely resist imposing costs on factories, but greater public scrutiny and higher-level government attention may be able to counteract local protectionism."

At the same time, China's environmental problems are decades old, said Mr Ma Jun, Beijing-based director of the Institute of Public and Environmental Affairs, a non-governmental organisation. "These are very deep-rooted problems. There is no silver bullet," said Mr Ma.