Railway operators in Japan will restrict certain hazardous materials from being carried on board as part of a move to bolster security ahead of the 2025 Osaka Expo.

The Japan Private Railway Association, a group of 73 operators, and six JR companies plan to expand the list of restricted items to include materials such as flammable liquids, high-pressure gases, explosives, poisons and pesticides, the transport ministry said Tuesday.

The ministry ordered all railway companies to revise their anti-terrorism guidelines and ban hazardous chemicals that are currently allowed to be brought on board under certain conditions.

Under the new guidelines, sulfuric acid and hydrochloric acid ¡ª currently allowed if they are in a sealed container ¡ª would be banned, with the exception of items such as battery acid or strong toilet detergents.

However, the new restrictions will be difficult to enforce as there will be no X-rays or other security checks. Instead, the railway association plans to put up posters to raise awareness of the new rules.

The new measures will take effect in April. The Osaka Expo will run for six months from April 13.

Dangerous incidents involving hazardous materials on trains have happened before. In October 2023, a passenger accidentally spilled sulfuric acid while on the Tohoku Shinkansen Line, resulting in six people being taken to hospital, with four experiencing burns.

The passenger, who was the head of a geological survey company, had brought the chemical solution from a warehouse in Aomori Prefecture, but the plastic bottle he used melted, causing the leak.

Regulating what can be brought on board has long been an issue in Japan, with the rare accident or crime always making headlines. Famous cases include a self-immolation on a bullet train in 2015, a 2018 knife attack, as well as several attacks on trains in Tokyo, including the 1995 sarin attack on the capital¡¯s subway.

Implementing stronger safety measures on trains has proven difficult due to their widespread use. Baggage inspections, for example, would make the transportation system inefficient and has thus been deemed an unrealistic option.

Some railway companies have increased the number of station security staff and installed security cameras on trains in hopes of deterring violence or misbehavior.