Beautiful sunsets or the alarming glow of pollution?

Have you strolled on East Sands in the evening, watching the blue sky turn into vivid yellow and orange arrays? Major cities have some of the most dazzling sunsets, and although they are a beautiful sight, they also reveal deeper environmental issues. Pollution from our transportation and industry, along with the increasing number of wildfires, doesn't just contribute to melting ice caps — it also influences the way light scatters in our atmosphere, altering the appearance of sunsets.

The blue sky that we observe daily is the result of Rayleigh scattering. The molecules in the atmosphere are much smaller than the wavelength of the light radiation. The sun emits white light, which is all the wavelengths combined. When the white light hits the particles in the atmosphere, it scatters depending on the wavelength. Rayleigh scattering increases when the wavelength decreases; blue and violet light have the shortest wavelengths and will therefore scatter the most, resulting in our blue sky. During sunrise and sunset, the sun is at an angle relative to its original position, meaning that the light has to travel farther. Due to blue light being already scattered, orange and red light reach us.  

In scattering, not only does the wavelength of the light matter, but the surrounding particles as well. Earth’s typical atmosphere is primarily composed of nitrogen and oxygen gas, with only 0.042 per cent being carbon dioxide. In altered environments, such as an area near a wildfire, excess aerosol particles will be present. Light travels through a thicker column of air before it reaches us for sunrises and sunsets; this excess in particles has the same effect and also results in an orange or red sky. 

The soot and smoke from wildfires can travel over a large area, effectively blanketing and filtering the light. However, wildfires are not the only contributors to this effect; human-caused air pollution — primarily from transportation emissions and the burning of fossil fuels for energy — is also a major factor. Pollutants can react with the air to create bigger molecules, which scatter the light in different directions from the small nitrogen and oxygen molecules. 

Don’t be fooled by the beautiful colours they produce — these particles have a severe effect not only on animals and plants, but on humans too. Respiratory and cardiovascular diseases, and their related cancers, are closely associated with both short and long-term exposure to high levels of air pollution. According to the World Health Organization (WHO), air pollution is the cause of 4.2 million premature deaths per year. The majority of these deaths are related to heart disease and strokes. One of these pollutants is sulfur dioxide, which is produced in the burning of fossil fuels. Besides being toxic, it also causes acid rain, affecting water environments and changing their pH levels. Sensitive species will struggle to adapt and may face extinction as a result.

Although sunsets are pretty to look at, they can also be red flags — literally — for environmental dangers. The particles responsible for their vibrant colours can indicate poor air quality and increased risk for serious health issues. Raising public awareness about the connection between ecological health and community well-being is essential for driving policy changes. By working together, we can ensure that our sunsets reflect beauty and a commitment to a healthier planet, benefiting all living beings on Earth.

Illustration by Isabelle Holloway