Qualité de l’air à Silao

What is the current level of air pollution in Silao?

Silao, officially Silao de la Victoria, is a city in the west-central part of the state of Guanajuato in Mexico. According to a census conducted in 2005, the estimated population was approximately 150,000 people. This ranks it as the seventh most populous community in the state.

At the beginning of 2022, according to data released on the IQAir website, Silao was going through a period of “Moderate” air quality with a US AQI reading of 80. This United States Air Quality Index number is calculated using the levels of six of the most prolific air pollutants, such as nitrogen dioxide, sulphur dioxide, ozone, carbon monoxide and both sizes of particulate matter, which are PM2.5 and PM10. It can then be used as the metric when comparing air quality in other cities around the world. If data is unavailable for all 6 pollutants, a figure can still be calculated by using what figures there are. There were three of the main pollutants measured in Silao which were; PM2.5 - 26 µg/m³, ozone (O₃) - 0 µg/m³ and sulphur dioxide (SO₂) - 0 µg/m³.

This level of PM2.5 is just over two and a half times over the recommended safe level of 10 µg/m³ as suggested by the World Health Organisation (WHO) as being an acceptable level. Although no amount of air pollution is considered to be safe.

When air pollution is from this “Moderate” bracket the given advice would be to remain indoors as much as possible, closing doors and windows to prevent the ingress of more polluted air. Those who are more sensitive to poor quality air should avoid venturing outside until it improves. If this is unavoidable, then a good quality face mask should be worn at all times. All types of outdoor exercise should be avoided until the air quality improves. There is a downloadable app from AirVisual.com which is suitable for all operating systems and gives the latest information regarding air quality in real-time.

Does the level of air pollution change much throughout the year in Silao?

The 2020 figures published by IQAir.com show that during August and September Silao achieved the WHO target figure of being less than 10 µg/m³. The respective figures were 7.9 and 8.3 µg/m³. The month of July saw “Good” quality air with a reading of 10.2 µg/m³. The remaining nine months of the year saw air quality from the “Moderate” category with figures between 12.1 and 35.4 µg/m³. There were no records about air quality kept before 2020 when a figure of 19 µg/m³ was recorded. This low figure was to be expected because it may have been affected by the COVID-19 pandemic as many vehicles were no longer in daily use because the offices were closed, in an attempt to halt the spread of the virus. Many factories and non-essential production units were also required to close which removed their emissions from the atmosphere, albeit on a temporary basis. Worldwide, cities reported a much better quality of air due to the general lack of traffic pollution in city centres due to the pandemic.

Is there a main source of air pollution in Silao?

Transportation is an important tool for the development of productive activities in the entity. Derived from daily use, the consumption of fuels increases, which in turn generate pollutant emissions that contribute to the deterioration of environmental quality and accelerate the effects of climate change.

Silao is the sixth most polluted city in Mexico because around 600 brickyards release large volumes of toxic gases. However, they are willing to work with the authorities to reverse the problem.

To make clay partitions, producers burn firewood, tannery waste, plastics of all kinds and hazardous waste such as spent oils, which during combustion generate enormous amounts of toxins such as dioxins and furans, nitrogen oxides, carbon monoxide, sulphur oxides and black carbon as particulate material PM2.5 and PM10, pollutants that cause irreversible diseases.

The combustion of wood alone releases into the atmosphere more than 102,000 tons of carbon dioxide and 330 tons of methane a year which are both greenhouse gases. For every 100 fires carried out per week, around 2.5 tons of wood are needed with a traditional oven.

The authorities allow the brickmakers to burn pallets, the remains of packaging from different industries such as the shoe and automotive industries, and of course the remains of the tanneries that have traces of glue and paint. There is no real control by the environmental and municipal authorities, they do not have enough inspectors and in the end all kinds of burning are allowed.

Can anything be done to improve air quality in Silao?

Atmospheric monitoring is one of the main indicators of air quality, it also represents a valuable management tool to implement actions for the prevention and control of pollutants present in the atmosphere, in the face of conditions that put the health of citizens at risk. In addition, it is a source of information for citizens on pollution levels.

What are the detrimental effects of breathing in polluted air?

Air pollution is a global problem, but it does not affect everyone equally. In highly urbanized areas there are groups with greater vulnerability, for example all those who suffer from cardiovascular and respiratory diseases, the population sensitive and reactive to allergies that affect the respiratory tract, new-borns and the elderly.

High levels of nitrogen dioxide and carbon dioxide can cause mucosal irritation in the respiratory tract, which can lead to episodes of coughing and difficulty breathing. It also increases the chances of developing respiratory infections or allergic reactions and aggravates cardiovascular diseases.

A pathway to damage opens up when smaller particles find their way to the deepest parts of the lungs, the alveoli, where oxygen is transferred to the bloodstream. It has been established that PM2.5 particles are small enough to be part of this transfer, entering the cardiovascular system and circulating throughout the body. The risks of this include the potential to block arteries, increasing the risk of strokes, as well as cardiovascular disease and heart attacks.

There's also evidence that the particles can reach the brain, so scientists are investigating the potential effects on conditions like dementia.