Green
Understanding How the Air Quality Index Works
Understanding How the Air Quality Index Works
Air quality levels have received a lot of attention in recent months.
In the wake of COVID-19 lockdowns, many places reported a marked increase in air quality. Northern India captured the world’s attention when it was reported that the Himalayan mountain range was visible for the first time in decades.
On the flipside, later in the summer, wildfires swept over the Pacific Northwest and California, blanketing entire regions with a thick shroud of smoke that spanned hundreds of miles.
How is air quality measured, and what goes into the health scores we see?
Measuring the Air Quality Index
When we see that air quality is “good” or “unhealthy”, those public health categories are derived from the Air Quality Index (AQI).
In the U.S., the AQI is calculated using five major air pollutants regulated by the Clean Air Act:
- Ground-level ozone
- Carbon monoxide
- Sulfur dioxide
- Particle pollution, also known as particulate matter
- Nitrogen dioxide
Some countries have a slightly different way of calculating their scores. For example, India also measures levels of ammonia and lead in the air.
To make these readings more accessible, the AQI has a scoring system that runs from 0 to 500, using data collected from air monitoring stations in cities around the world. Scores below 50 are considered good, with very little impact to human health. The higher the score gets, the worse the air quality is.
To make communicating potential health risks to the public even easier, ranges of scores have been organized into descriptive categories.
| AQI Score Range | AQI Category | PM2.5 (μg/m³) | Health Risks |
|---|---|---|---|
| 0-50 | Good | 0-12.0 | Air quality is satisfactory and poses little or no risk. |
| 51-100 | Moderate | 12.1-35.4 | Sensitive individuals should avoid outdoor activity. |
| 101-150 | Unhealthy | 35.5-55.4 | General public and sensitive individuals in particular are at risk to experience irritation and respiratory problems. |
| 151-200 | Unhealthy | 55.5-150.4 | Increased likelihood of adverse effects and aggravation to the heart and lungs among general public. |
| 201-300 | Very Unhealthy | 150.5-250.4 | General public will be noticeably affected. Sensitive groups should restrict outdoor activities. |
| 301+ | Hazardous | 250.5+ | General public is at high risk to experience strong irritations and adverse health effects. Everyone should avoid outdoor activities. |
Particulate Matter
While all the forms of atmospheric pollution are a cause for concern, it’s the smaller 2.5μm particles that get the most attention. For one, we can see visible evidence in the form of haze and smoke when PM2.5 levels increase. As well, these fine particles have a much easier time entering our bodies via breathing.
There are a number of factors that can increase the concentration of a region’s particulate matter. Some common examples include:
- Coal-fired power stations
- Cooking stoves (Many people around the world burn organic material for cooking and heating)
- Smoke from wildfires and slash-and-burn land clearing
Wildfires and Air Quality
Air quality scores can fluctuate a lot from season to season. For example, regions that are reliant on coal for power generation tend to see AQI score spikes during peak periods.
One of the biggest fluctuations occurs during wildfire season, when places that typically have scores in the “good” category can see scores reach unsafe levels. In 2020, Eastern Australia and the West Coast of the U.S. both saw massive drops in air quality during their respective wildfire seasons.
Luckily, while these types of fluctuations are extreme, they are also temporary.
Correction: Graphics and article updated to include nitrogen dioxide.
Agriculture
Fertilizer: Why it’s More Important than You Think
Fertilizer usage dates back to as early as 6,000 to 2,400 BC and remains just as crucial for crop production today.
Fertilizer: Why It’s More Important Than You think
The global population is expected to reach nearly 10 billion people by 2050. So, in order to feed our growing world sustainably, increased crop production is essential.
Over recent decades, farmers have been able to more than double their production of crops thanks to fertilizers and the vital nutrients they contain.
When crops are harvested, the essential nutrients are taken away with them to the dining table, resulting in the depletion of these nutrients in the soil. To replenish these nutrients, fertilizers are needed, and the cycle continues.
The above infographic by Brazil Potash shows the role that each macronutrient plays in growing healthy, high-yielding crops.
Food for Growth
Nitrogen, phosphorus, and potassium (NPK) are three primary macronutrients that are the building blocks of the global fertilizer industry. Each plays a key role in plant nutrition and promoting crop growth with higher yields.
Let’s take a look at how each macronutrient affects plant growth.
| Nutrient | Why it’s needed? | What does it do? | What happens without it? |
|---|---|---|---|
| Nitrogen (N) | Needed for the formation of all plant and animal proteins. | Nitrogen ensures that energy is available when and where it is needed to maximize yield and regulate water and nutrient uptake. | Nitrogen deficiency in crops causes stunted and spindly plants, low protein content in seed and vegetative parts, and fewer leaves. |
| Phosphorus (P) | Vital for plant photosynthesis. | Phosphorus allows plants to convert the sun’s energy into food, fiber, and oil. It improves how efficiently the plant absorbs water and macronutrients such as nitrogen. | Phosphorus deficiency causes stunted growth, reduced crop yields, low quality harvests, and moisture stress. |
| Potassium (K) | Essential for robust high quality crops. | Potassium helps regulate water pressure in plant cells and maximizes crop yields by strengthening plant stems to make them more resilient to drought, flooding, and temperature swings. | Potassium deficiency causes a slower growth rate of plants, delayed pollination and maturity, underdeveloped leaves, reduced crop yields, weakened stalks, and moisture stress. |
If crops lack NPK macronutrients, they become vulnerable to various stresses caused by weather conditions, pests, and diseases. Therefore, it is crucial to maintain a balance of all three macronutrients for the production of healthy, high-yielding crops.
The Importance of Fertilizers
Humans identified the importance of using fertilizers, such as manure, to nourish crops dating back to nearly 6,000 to 2,400 BC.
As agriculture became more intensive and large-scale, farmers began to experiment with different types of fertilizers. Today advanced chemical fertilizers are used across the globe to enhance global crop production.
There are a myriad of factors that affect soil type, and so the farmable land must have a healthy balance of all three macronutrients to support high-yielding, healthy crops. Consequently, arable land around the world varies in the amount and type of fertilizer it needs.
Fertilizers play an integral role in strengthening food security, and a supply of locally available fertilizer is needed in supporting global food systems in an ever-growing world.
Brazil is one of the largest exporters of agricultural goods in the world. However, the country is vulnerable as it relies on importing more than 95% of its potash to support crop growth.
Brazil Potash is developing a new potash project in Brazil to ensure a stable domestic source of this nutrient-rich fertilizer critical for global food security.
Click here to learn more about fertilizer and food production in Brazil.
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