Overwork has been the main culprit to blame for the deaths of police officers on duty in the Chinese mainland in the past five years, according to the Ministry of Public Security.

Since 2006, 47 percent of the 2,182 officers who died on duty died from overwork, while those who work in the front lines of law enforcement, such as traffic officers and officers at local police stations, suffered the greatest number of sudden deaths.

"The Labor Law mandates an 8-hour work day, but police officers work much longer," Dai Peng, dean of the investigation department of the Beijing-based Chinese People's Public Security University, told China Daily on Monday. "It's especially true of those who work in the front lines and are subject to prolonged intensive stresses that have seriously affected their physical and psychological health."

A survey conducted throughout the country in 2005 showed that police officers usually work from 11 hours to 15 hours a day and often have only one day off after three weeks of work.

According to Wang Dawei, a professor at the university, Western countries have an average of 35 police officers for every 10,000 of their citizens. China, in contrast, only has 11 officers for every 10,000 citizens.

"One police officer in China shoulders the workload of three police officers (in the West)," Wang told Globe Magazine, which is based in Beijing. "So they couldn't be more tired."

Shen Zhandong, a policeman from Zhengzhou, capital of Henan province, died from overwork on his 28th birthday, when he was on duty in Urumqi, capital of the Xinjiang Uygur autonomous region.

At 10 pm, Jan 29, 2010, Shen went back to his dormitory after a day spent patrolling. His colleague, just finishing a discussion about a work schedule for the next day, found Shen at 11:40 pm lying on the bed, motionless.

First aid was given to Shen, but his life was not saved. Doctors later announced the sudden death had been the result of overwork.

A lack of police personnel has been a long-standing issue in China. Take Guangdong province, which, according to Nanfang City News, has 120,000 police officers serving a population of more than 100 million.

"There are 730 police officers in our district, including traffic officers, public security officers, criminal investigators, and officers in local police stations," said a policeman who works in a police substation in the province. "But we are in charge of nearly 400 square kilometers."

"We worked around the clock in the second half of 2010 to provide security for the Asian Games. When others enjoy holidays, we burn the midnight oil in police stations."

Dai Peng said one way to improve the situation would be to better allocate police resource and eliminate the discrepancies in duties between police personnel who stay in the office, who often enjoy leisure, and those on the front lines, who frequently are overburdened.

"Finding more police officers to work in the front lines has been a large difficulty for public security authorities," Dai said. "At the same time, new police officers should be drawn every year from the armed forces, police-training schools and general society, in accordance with a place's local population, logistics, and geographic conditions."

Overwork was not the sole cause of police officers' deaths, according to the Ministry of Public Security. Many others died while fighting with criminals or from traffic crashes that occurred while they were performing their duties, accounting for 36.4 percent of the police officer deaths that have occurred since 2006.

"The lack of protective equipment for police officers and the many (legal) constraints they are subject to lead to frequent attacks on the police," said the policeman in Guangzhou.

Experts said there is a need for more protective equipment in less-developed regions.

"More importantly, police officers should thoroughly learn the laws that regulate what they can do when fighting criminals and become better at subduing criminals while protecting themselves."