Qualité de l’air à Shasta Lake

Is Shasta Lake badly polluted?

Shasta Lake has shown some sizeable elevations in its pollution readings in the months of July and August of 2021, as well as certain months of 2020 also having had higher levels of pollution, due to the extreme nature of the wildfires that took place in the latter period of the year.

In mid-August of 2021, Shasta Lake presented with a US AQI reading of 474, a serious level of air pollution that placed the city into the hazardous air quality rating bracket, color-coded as maroon and requiring a US AQI reading of 301 or above to be classified as such. this is the highest air pollution rating bracket available, and as the name suggests, puts the general public at high risk of serious conditions occurring. Other elevated readings taken around the same period include US AQI figures of 365, 246 and 156, all of which still fall into the dangerous category of air pollution levels.

At the time in which the above-mentioned figure of 474 was recorded, Shasta Lake was found to have a PM2.5 count 46 times higher than the World Health Organization's (WHO's) exposure recommendation, putting those who are living in direct vicinity at a very high risk of being subject to many health issues, some of which will be discussed later in the article. Whilst there are many months on record in times past that show that Shasta Lake can have respectable levels of air quality during certain months, the forest fires or wildfires are responsible for creating these extremes in pollution readings, and thus Shasta Lake can be considered highly polluted due to its susceptibility to extreme pollution accumulations from wildfires.

Why is the air so polluted in Shasta Lake?

Besides the aforementioned wildfires causing the heightened levels of air pollution, there are still other sources that can cause the year-round ambient readings to increase. With any level of human or industrial activity comes polluting sources, due to processes such as combustion taking place in many factories, power plants and even car engines, giving out their own forms of chemical pollutants and fine particles.

As mentioned, vehicles would be a contributing factor to rising air pollution levels in Shasta Lake and throughout the whole of California. A variety of these vehicles include ones such as cars and motorbikes, along with heavy freight vehicles used for transporting industrial goods and other produce. These include trucks and lorries, as well as certain buses.

Many vehicles throughout certain areas in California still use diesel as their main fuel source and can give out the large number of pollutants that arise from the combustion of fossil fuels. Furthermore, vehicles can contribute to the release of many tons of rubber particles, caused by the residual wear and tear of tire treads. These rubber particles enter into the atmosphere and cause further health problems when inhaled, as well as gathering on topsoil or in bodies of water, causing environmental damage and harm to various ecosystems.

As mentioned, smoke from wildfires is the biggest offender in causing air pollution levels to rise, and although they are not a constant occurrence throughout the year, the readings on record in 2020, as well as the ones currently occurring in mid-2021 show that they can cause severe cases of air pollution to happen, being far more dangerous as a pollution source than any others that have been mentioned.

PM2.5 refers to particulate matter that is 2.5 micrometers or less in diameter, making it 30 times smaller than the width of a human hair. Due to this size factor (as well as being able to go down to ultrafine sizes many microns smaller), it can penetrate deep into the lungs upon inhalation, causing a whole host of health issues to appear. Furthermore, it can cross into the bloodstream due to its minute size, making it one of the most dangerous pollutants found in the air, both in Shasta Lake and throughout the United States. Other sources that continuously add to the air pollution levels would be ones such as factories, along with power plants and various industrial sites also contributing, with many of them using fossil fuels such as coal, oil, natural gas and diesel to provide their energy.

These sources present through many areas in California and the United States and may cause elevations of pollution to be concentrated around their nearby vicinity, although large amounts of sprawling or vacant land in California can put adequate distance between polluting industrial sites and human populations. However, this can differ in some areas, with poorer portions of the population often being situated right next to industrial sites and developments.

The issue of thermal inversion also has its part to play in pollution buildups throughout California. With colder air having a higher density to it, and many Californian cities being tucked in between mountain ranges and valleys, it can remain trapped at ground level with the air above staying warm, causing the whole cycle to repeat and leaving pollutants stuck at ground level, unable to rise into the upper levels of the atmosphere whereby they can safely disperse, far away from potential exposure to the population below. As mentioned, the natural topography of the state of California can assist greatly in this issue. Coupled with the large number of forest fires currently taking place, as well as ones from years past, particularly the late 2020 forest fires ravaging much of the state, California is thus subject to its high pollution levels, reaching dangerous levels when all of these conditions are met.

What are some health issues that can be caused by pollution exposure in Shasta Lake?

Several of the months in Shasta Lake taken from years past have shown to have more respectable levels of air cleanliness, which will be mentioned in further detail later in the article. Whilst certain months from times past have fallen well within the WHO's target goal for optimal air quality, it still stands to reason that air pollution may occur within localized areas, with clouds of smoke, haze and fine particles accumulating due to a combination of circumstances, with anthropogenic or human-based activities, as well as industrial activity meeting with the perfect weather conditions for pollution build-up.

This can result in situations whereby pollution can accumulate over several days or weeks before it is blown away by prevailing winds, with rain being another pertinent factor in cleaning the air of pollutants (although of note is that strong wind remains the best way in which pollution is removed from the air, with rain mostly being able to only tamp down larger particles that permeate the air. Due to their larger diameter, they present much less of a risk to human health than their smaller or ultrafine counterparts do.) In addition, there are many groups of people within Shasta Lake and much of California that are at far greater risk and more susceptible to the hazardous effects that pollution exposure can bring about.

These sensitive or at-risk people include those who are more likely to fall foul to the various illnesses brought on by excessive breathing of chemicals in the air, ultrafine particles and other air contaminants. These include groups such as young children or babies, as well as the elderly. The elderly are particularly susceptible to incurring damage from breathing pollutants. For this demographic, respiratory infections or mild coughs can often develop into more life-threatening issues, particularly during the more polluted months of the year. Others include those who have a poor level of health, worsened many times through certain lifestyle choices such as being sedentary, not partaking in exercise or smoking.

Others include those that have pre-existing health conditions or compromised immune systems. Certain individuals also have a hypersensitive reaction towards chemical pollutants or fine particles, causing aggravated skin or respiratory reactions. As these are some of the more vulnerable groups that should take extra care, of note is that no individuals amongst a population are truly safe from higher levels of pollution exposure.

These are cases such as dry coughs, chest pains and subsequent mild infections of the respiratory tract. These will generally disappear, or at least go down in severity when exposure to pollution is ceased. Referring to PM2.5 and its danger to the wellbeing of the public, PM2.5 is any material that is 2.5 micrometers or less in diameter, making it roughly 30 times smaller than the width of a human hair. This extremely small size gives it the ability to bypass the body's defense system and to penetrate deep into the tissue of the lungs upon inhalation. From there, it can cause inflammation of the lung tissue, along with scarring and irritation of the respiratory tract. Once in the lungs, it can make its way further into the bloodstream due to its size giving it the ability to cross the blood barrier, via the alveoli or small air sacs in the lungs.

Once these ultrafine particles are in the bloodstream, they can cause several serious conditions, ranging from damaged blood vessels, along with increased risks of cancer, particularly of the lungs due to many of these particles remaining lodged there. PM2.5 can be comprised of materials such as nitrates and sulfates, metals, dust and soot, along with other finely ground materials such silica or gravel. Liquids such as water vapor, along with mold spores, fungi, bacteria and other hazardous inorganic materials or microorganisms can all make up the PM2.5 collective, depending on the size they reach.

Many of these are known to have salient carcinogenic properties (in particular soot, which is formed mainly from black carbon, released in vast quantities from forest fires, along with factories and industrial sites. Car engines can also release these via their exhaust. Due to the prevalence of its release from forest fires, black carbon would present a large amount of danger to those living in Shasta Lake during the times that the worst of the forest fires are taking place.

Other health issues include skin conditions such as atopic dermatitis, severe cases of acne, psoriasis as well as other aggravated rashes such as eczema, which can flare up during bouts of high pollution levels due to fine particles clogging skin pores, as well as certain chemicals causing skin irritation. Chronic obstructive pulmonary disease (COPD) will often make itself present it. COPD is an umbrella term that pertains to a multitude of various respiratory conditions, which include pneumonia, aggravated forms of asthma, along with bronchitis and emphysema.

In more chronic or drawn-out cases (whereby exposure takes place over long periods), conditions such as ischemic heart disease begin to present themselves, particularly amongst the susceptible portions of the population.

This occurs when the heart tissue sustains damage due to an inadequate supply of oxygen. Instances of heart attacks can also go up, along with the chance of strokes, arrhythmias, nausea and headaches, along with death. High exposure to pollution has a direct correlation to increased mortality rates, and as such, during bouts of high pollution, many preventative measures should be employed to avert any potential damage that can be incurred. These include avoiding outdoor activities and exercise (which can raise breathing rate and thus increase the number of pollutants that one can breathe), along with wearing fine particle filtering masks.

Doors and windows can be closed to prevent indoor air pollution levels from rising excessively, and air purifiers can also be run if they are available. These will all be shown on the air quality graph on this page, along with the opposite during bouts of cleaner air, encouraging users to partake in outdoor activities. The air quality graphs, forecasts and maps present on this page can also be accessed via the AirVisual app, both of which are encouraged for individuals who may need to keep their pollution exposure level as low as possible.

When do pollution levels reach their highest in Shasta Lake?

Observing the air quality levels present throughout 2020, it can be seen that Shasta Lake had its worst levels of air quality from August through to December, along with January and February also showing signs of elevated air pollution levels. Whilst the forest fires that occurred have skewed results and these months may not be indicative for true year-round readings, it still stands to reason that they may indicate a pattern and time of year in which the pollution levels rise to their highest, along with the time in which forest fires are most likely to occur.

The readings taken from August through to December were 30.6 μg/m³, 53.5 μg/m³, 20 μg/m³, 10.4 μg/m³ and 11.1 μg/m³ respectively. January and February also had mildly elevated readings of 15 μg/m³ and 11 μg/m³.

This placed the months of January, August and October into the 'moderate' pollution rating bracket, which requires a PM2.5 reading of 12.1 to 35.4 μg/m³ to be classified as such, also color-coded as yellow. February, November and December fell into the 'good' air quality rating bracket, which requires a reading between 10 to 12 μg/m³, and represents a better level of air cleanliness, as the name and fine margin of entry would indicate.

September was the most polluted month of the year with its reading of 53.5 μg/m³, placing it within the 'unhealthy for sensitive groups' bracket, the only month of the year to do so. The air quality at this time would cause the general public to suffer from respiratory irritation and aggravation of certain conditions, whilst the aforementioned vulnerable groups would suffer from a wider range of ill health effects.

At what time of the year is the air safer to breathe in Shasta Lake?

Using the air quality readings taken for 2020 once again as a reference point, Shasta Lake had its best air quality readings present from March through to July. These all fell within the WHO's target for the best level of air quality at 10 μg/m³ or less, with the closer to 0 being the most optimal.

Their readings were 6.7 μg/m³, 5 μg/m³, 3.6 μg/m³, 3.4 μg/m³ and 8.1 μg/m³ respectively, placing both May and June into the cleanest positions of the year with their readings of 3.6 μg/m³ and 3.4 μg/m³. The air quality at such times would be significantly freer from clouds of smoke, haze and noxious ultrafine particles or chemical contaminants, caused mainly by the occurrences of forest fires, along with the anthropogenic and industrial activities taking place.