The South Korean government Tuesday denied local rumors that toxic chemicals from the Tianjin blast in China may affect the peninsula.

Unidentified online rumors have spread in the country that the toxic substance allegedly leaked from the Chinese blast site last week would likely affect the peninsula. The postings included those who claimed the U.S. Embassy in China had warned people to avoid exposure to the rain as sodium cyanide has leaked into the air.

On Sunday, Beijing news outlets reported that Chinese officials had discovered about 700 tons of sodium cyanide was stored at the explosion site, stoking public concerns over the possible leak due to the explosions.

Water-soluble solid sodium cyanide forms hydrogen cyanide if treated with acid. The exposure to hydrogen cyanide can cause burns, dermatitis, headaches and even death.

The sudden issuance of the ultrafine dust alert over the weekend in Korea added fuel to the rumors that the country would be hit by the toxic chemicals from China.

On Sunday morning, the ultrafine dust advisory was raised in Seoul and Incheon for over six hours as the hourly average ultrafine dust concentration exceeded 120 micrograms per cubic meter for more than two hours. The alert was lifted later in the afternoon.

The Environment Ministry, however, said the sodium cyanide spreading to Korea is geographically nearly impossible.

“Tianjin is 800 kilometers away from Seoul, which is too far to be affected,” said the ministry.

Experts also played down the concerns, citing the characteristics of the toxic substance.

“Sodium cyanide is naturally heavier than air. Therefore, it’s nearly impossible to spread through the wind over hundreds of kilometers,” chemistry professor Lee Chong-soon at Yeungnam University told The Korea Herald.

The weather data of the blast day also showed little chance of it spreading.

“On Aug. 12, the wind of the concerned region headed from south to southwest, according to the data. This indicates that the wind actually blew in the opposite direction of the peninsula,” said Korea Meteorological Agency officials.

Meanwhile, the Ministry of Public Safety and Security vowed to carry out an emergency safety inspection on a number of factories and ports that deal with harmful chemical substances as part of its efforts to prevent similar accidents and alleviate public concerns.

The safety inspections will be conducted with municipal firefighting departments and four ministries, including the Environment Ministry and Labor and Employment Ministry, the authorities said.

It will also hold a group meeting Thursday to review the preventive measures and accident response manuals, they added.

By Lee Hyun-jeong (rene@heraldcorp.com)