What is a pollution peak?

Summary

There is an increasing frequency of « pollution peaks » throughout the world. But what are they, exactly? Let’s find out…

16Juin.
1

According to the annual air quality assessment in the Ile-de-France published on May 19 by the monitoring body Airparif, more than 2.3 million people in the Greater Paris area are exposed to fine particle pollution levels that flout current regulations. This is a worrying figure, and the numerous alerts to air pollution registered throughout April in the Paris region remind us of the practical implications in terms of public health. We shed light on these alarming phenomena at the root of current environmental and regulatory problems.

When a certain threshold is crossed

It is very difficult to gauge how serious atmospheric pollution is on a global scale.

From Delhi to Mexico, « pollution peak » alerts increase every year. The severity of these episodes is assessed using the World Air Quality Index (WAQI): a scale of 0 to 500, which shows peaks in real time. However, as environmental standards for industrial production and energy are subject to different levels of stringency from one country to another, it is very difficult to gauge how serious atmospheric pollution is on a global scale.

More pollutants in the air creates a risk for health and the environment, and requires the relevant authorities to take measures to reduce atmospheric pollution.

So when do we talk of a « pollution peak »? A « peak » is when an excessive quantity of one or more pollutants in the air creates a risk for health and the environment, and requires the relevant authorities to take measures to reduce atmospheric pollution. In Europe, several pollutants are monitored. First of all, fine particles (micro-particles with a diameter of less than 0.25 micrometers, which are present more or less permanently in the atmosphere): there must be no more than 50μg/m3 in one day, for over 35 days. And yet the Paris beltway exceeded this for more than one hundred days in 2013! At 80 μg/m3, an alert is issued, and measures become stricter, including reduced speed limits, alternating circulation and possibly the prohibition of vehicles. Other pollutants in the sight lines are gases: nitrogen dioxide (no more than 200 μg/min one hour, for over 18 hours per year, as it is an irritant gas), as well as ozone and carbon monoxide.

Chronic causes

Air pollution is largely caused by road traffic.

Where does this pollution come from? « We both import it and export it, » says Pierre Emmanuel Burg of Air Parif, which participates in Esmeralda, the joint forecasting platform run by the air quality monitoring associations. « Near the main traffic thoroughfares, air pollution is largely caused by road traffic. Elsewhere, it is due to our everyday activities, like transport, farming and wood-heating. » And it is also found in our households.

« Given the extent of pollution, measures like alternating traffic are not enough, » says Sébastien Vray, spokesman for the Respire association, « even if they do reduce the concentration of pollutants on beltways and roadside areas. We can get back down to levels below alert thresholds, but if we don’t act on the chronic causes of pollution on a global scale, people’s health will continue to suffer. »

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