Salt available on the shelves of city supermarkets may be getting a tweak depending on the results of an upcoming survey.

According to the Beijing Center for Disease Control and Prevention (CDC), the survey to be held later this year into the health of Beijingers' thyroid glands may result in changes to the city's salt composition.

Li Yanghua, from the Beijing CDC Iodine Deficiency Disorders (IDD) project, said the medical check into thyroid gland disease will include a look at the presence of thyroid nodules, hyperthyroidism and other thyroid linked disorders.

"We will draw up a scientific plan and invite experts to give guidance," Li said. "But another survey conducted during the first half of this year shows that the iodine level in the city is just above the national standard, which means the future adjustment might only be a slight one."

A CDC survey in 2009 looked at urinary iodine levels among about 13,000 local people. The result indicated that the urinary iodine level was just above the international level of 200g/L (1000g=1mg).

The Ministry of Health released a document in July saying that iodine in edible salt should be reduced. According to the new standard, the lowest level of iodine in edible salt will remain at 20mg/L but the maximum amount will be reduced from 60mg/L to 30mg/L.

Chen Zupei, an official from the Ministry of Health who is responsible for the new iodine standard, said the need to reduce the amount of iodine in salt was not because the current level is dangerous but because it is higher than the healthiest level.

According to the standard of the World Health Organization, urinary iodine levels over 300g/L are excessive. Levels between 200 and 300g/L are sufficient.

"And the amount between 100 and 200g/L is considered to be ideal, which is what we are planning to do," Chen said.

Still, some residents were concerned that they might have been ingesting too much iodine.

"Although we've known that eating enough iodine can prevent us from getting hyperthyroidism, I also read some articles, saying that eating too much iodine can also lead to some thyroid gland diseases," said Yu Xiaodong, a 42-year-old resident living in Shijingshan district.

He said his wife suggested that they buy salt without iodine.

However, Li said the current level of iodine in edible salt, even though it will be lowered, is not dangerous to the health.

"There's no need to be worried about your health condition or change your diet because of the results of the survey," Li said.

"Even if the iodine level in salt was left the same as it is now, you will not get a health problem or become sick as a result."

He said eating as much as 600g of iodine a day is safe for a person weighing 60kg.

"The average iodine intake for a person in the city is less than 400g, which is absolutely safe," he added.