The most polluted air on ... early morning

Scientists warn cities with growing industries and transportation, early morning air is not only unwholesome but also very polluted.

Morning fitness hours in the city usually start at 5 o'clock. People poured into parks, sidewalks to exercise, or jogged the streets with little traffic, and took in the fresh air.

Mr. Nguyen Van Tien, 76, often walks around Thong Nhat Park (Hanoi) every morning, saying: 'I mobilize the whole family to exercise in the morning because at that time there are few people and few means of transport. pine, fresh air is very good for health '.

Smoke in industrial parks has seriously affected the environment (Photo: Tienphong)

However, Mr. Tien's judgment as well as many people in general may have to change in an increasingly degraded environment at an alarming level. Many scientists warn, early morning exercise in urban areas may also affect health because this time the air is most polluted.

Assoc. Dr. Nguyen Huu Chien, Head of the Department of Natural and Environmental Management - Can Tho University, affirmed: 'We are facing the risk of pollution in low-floor air masses at midnight and early morning. in urban and industrial areas and especially roads with heavy traffic. '

According to Dr. Chien, the freshness of the air is determined by the composition of substances in the air, especially those harmful to the human body. In the daytime, the sun makes the air temperature rise, the smoke of factories, vehicles and sand and dirt from rolling vehicles hovering in the air. When the sun goes down, the air temperature decreases. Over night, the ground is cooler. The heat radiating into the air a few hundred meters from the ground formed the upper air floor that was hot and cold, like a pot facing the ground.

At this time, the exhaust fumes of the factories could not be lifted high to radiate into the cloud layer but only viciously near the ground with a concentration at a time of concentration. If the ground becomes more and more calm, the level of air pollution increases.

In the winter, the northeast monsoon, heat-up due to nocturnal radiation can cause pollutants at this time to 2-3 times higher than the day. This phenomenon may last until early morning.

That's because the air layer temperature a few hundred meters above the ground increases with altitude, which is different from the usual situation that the higher the temperature, the lower. It is warmer in the daytime, heating the ground, dark to the ground still warm, emitting infrared radiation. Water vapor and CO ₂ absorb them, causing the air to warm up and the air temperature increases with altitudes up to several hundred meters. Late in the night, this heat-up class gets higher and can disappear after sunrise.

So scientists recommend that residents of industrial cities should shift their exercise time and physical training from early morning to around ten in the morning and three in the afternoon to be the most appropriate.

My Hang

According to the Hanoi Department of Natural Resources, Environment and Housing, Hanoi's air environment is heavily polluted, polluting toxic gases that have occurred locally.At present, the city has an average dust concentration of 1.5 to 3 times higher than the permitted standard, in which new urban areas are under construction and some roads for transportation of construction materials, dust concentration is 7 - 10 times.

The Hanoi National University of Civil Engineering has conducted a specific survey over the past 10 years and shows that the total amount of suspended dust caused by industry and handicrafts accounts for 67%, as the dirty streets account for nearly 30% and The rest is due to transport.In addition, emissions such as sulfur dioxide, carbon dioxide, methane . are also quite high and increase year by year.