"Prolonged air pollution will lower foreign companies' investment in Vietnam," Miura Nobufumi, chairman of Japanese Chamber of Commerce and Industry (JCCI) in Vietnam, told the forum on Friday.

Lower investment would lead to slower economic growth in the country, he said.

Water pollution is another major concern among overseas investors, with industrial and private discharge increasing river pollution beyond the national safety limit, he stressed.

The Vietnamese government should standardize and tighten environmental regulations as a matter of urgency, with Japan willing to provide technical assistance, it was added.

Vietnam’s biggest cities Ho Chi Minh and Hanoi last year regularly choked on haze, the air quality index (AQI) of each hitting very unhealthy levels.

Officials blame low air quality in both cities on construction, the growing number of cars and motorcycles and heavy industry, including steel works, cement factories and coal-fired plants.

Vietnam's GDP grew at 7.08 percent in 2018, the highest in a decade, to $223.9 billion. The country's economic growth reached 7.02 percent last year.