Air Pollutants: Petroleum Jelly Experiment Reveals The Invisible

Air pollution is a serious issue that can have detrimental effects on human health, especially for those suffering from asthma or allergies. It is important to understand the quality of the air we breathe and the pollutants that may be present. A simple experiment can be conducted to “see” air pollution and the presence of substances above natural levels in the air. This experiment involves the use of petroleum jelly, which is spread on clear plastic plates or containers and left in different locations, both indoors and outdoors, for 24 hours. The plates are then examined to observe and count the particulate matter that has landed and stuck to the jelly. By comparing the results from different areas, we can gain a better understanding of the air pollution in our surroundings and take steps towards improving air quality.

Comparing indoor and outdoor air pollution

The Earth has its own natural air-purifying technology that helps maintain relatively safe levels of air pollution in most parts of the world. However, indoor air pollution is often more severe than outdoor air pollution.

Outdoor air pollution is caused by emissions from various sources, including factories, fossil fuels, cars, and more, depending on the area. Natural sources of outdoor air pollution include construction and agricultural activities.

Indoor air pollution, on the other hand, is caused by dust, dirt, and other pollutants. It can be broken down into particle matter and gases. Particle matter includes soot and dust, while gases can include carbon monoxide, nitrogen oxide, and sulfur oxide. Inadequate ventilation can increase indoor air pollution by preventing clean air from entering the building. High temperatures and humidity can also raise the number of indoor air pollutants.

Interestingly, outdoor air pollution can infiltrate indoor spaces through open windows and doors, as well as cracks in walls and doors. This can be especially true during extreme air pollution events like wildfires.

While outdoor air pollution is a significant concern, it is important to also focus on indoor air quality, as we spend more than 90% of our time indoors. Several reports have shown that indoor air pollution levels can be 2-5 times higher than outdoor pollution levels and can even reach 100 times higher in certain cases.

To visually demonstrate the difference between indoor and outdoor air pollution, a simple experiment can be conducted using petroleum jelly. In this experiment, clear plastic containers or plates are labelled as "inside air" and "outside air". A layer of petroleum jelly is spread on the bottom of each container or plate, and they are placed in different locations, such as inside a classroom and outdoors. After 24 hours, the plates are examined to see the particulate matter that has accumulated, providing a visual representation of the air pollution in each location.

Observing air quality

Prepare the Materials

For this experiment, you will need clear plastic containers or plates, petroleum jelly, rubber gloves, a permanent marker, and masking tape or poster putty.

Set Up the Experiment

Using the marker, label each container or plate with different locations, such as various rooms in a house (bedroom, kitchen, basement) or "inside air" and "outside air". It is important to choose heavily populated areas to accurately assess indoor air quality. Wear rubber gloves and spread a thin, even layer of petroleum jelly on the bottom of each container or plate, ensuring the same amount for each.

Place the Containers or Plates

Use the masking tape or poster putty to hang the containers or plates on the walls of their respective rooms or designated areas. Leave them undisturbed for 24 hours.

Observe and Compare

After 24 hours, observe the petroleum jelly on each plate or container. Compare the results between the different locations. The petroleum jelly will capture and reveal particles present in the air, providing a visual representation of the air quality in each location.

Additionally, here are some other methods and tools to observe air quality:

• Air Quality Index (AQI): Developed by the EPA, the AQI is a tool to communicate outdoor air quality and its health implications. It ranges from 0 to 500, with higher values indicating increased pollution and health concerns. The AQI is categorised into six colour-coded categories to easily identify the level of air pollution.
• Satellite Monitoring: Satellites orbiting the Earth monitor the composition of the air, providing data on pollution levels.
• Human Observations: While subjective, human observations of haziness and visibility can provide some indication of air quality. Taking photographs of the horizon at the same location, time, and with consistent camera settings can help track changes in air quality over time. Additionally, noting the farthest landmark visible on a clear day compared to a hazy day can provide a basic understanding of air quality.
• Sun Photometer: This instrument provides a numerical measurement of the amount of light reaching the ground, which scientists relate to particle pollution. It offers a more precise way to gauge air quality beyond what is visible to the human eye.

Health effects of air pollution

Air pollution is a mixture of small particles (pollutants) that can have significant adverse effects on human health. These particles are commonly referred to as particulate matter (PM) and include dust, soot, and droplets of liquids. The size of these particles varies, with coarse particles measuring less than 10 microns in diameter and fine particles being less than 2.5 microns in diameter.

The sources of particulate matter are diverse, including factories, power plants, and vehicles that burn fossil fuels, such as diesel and gasoline-powered equipment. Additionally, natural sources like wildfires and wood-burning stoves contribute to particle pollution. These particles can directly enter the body through inhalation and cause a range of health issues.

One of the most concerning health impacts of air pollution is the increased risk of premature death. According to estimates, more than 4 million people worldwide die prematurely each year due to outdoor air pollution. The leading causes of these early deaths include stroke, heart disease, lung cancer, respiratory infections, and COPD. The deadly components of air pollution, such as ozone, nitrogen dioxide, and sulfur dioxide, play a significant role in these fatalities.

Air pollution also poses a threat to pregnant women and their unborn children. Exposure to polluted air can increase the level of toxic chemicals in a pregnant woman's blood, weakening her immune system and placenta, potentially leading to preterm birth or low birth weight. Furthermore, studies indicate that air pollution can negatively impact a child's brain development and behaviour.

The respiratory system is particularly vulnerable to the harmful effects of air pollution. Ozone, a powerful lung irritant, causes inflammation and damage to the delicate lining of the small airways, impacting multiple body systems. High ozone levels can lead to breathing problems, chest tightness, coughing, and shortness of breath, even in otherwise healthy young adults. Additionally, sulfur dioxide, a byproduct of burning fossil fuels containing sulfur, irritates the eyes, worsens asthma, and increases susceptibility to respiratory infections.

Another concerning health impact of air pollution is its contribution to cardiovascular issues. Tiny particles in the pollution can enter the bloodstream and cause inflammation, increasing the risk of heart attack, irregular heartbeat (arrhythmia), heart failure, and stroke. Black carbon, a component of particulate matter from burning fuel, is specifically linked to a higher risk of heart attacks and strokes.

Using a microscope to view particulate matter

To view particulate matter under a microscope, you can conduct a simple experiment using petroleum jelly. This experiment can help visualise air pollution and the presence of substances in the air.

First, take a permanent marker and label clear plastic containers or plates with different locations, such as various rooms in a house or "inside" and "outside". Then, spread a thin layer of petroleum jelly onto the bottom of each container or plate, ensuring an even layer. Place the containers in their respective locations, leaving them undisturbed for 24 hours.

After the allotted time, use a microscope to examine the petroleum jelly. Particulate matter will have adhered to the jelly, allowing you to observe it under magnification. This matter can include a mixture of solid particles and liquid droplets, with sizes varying from less than one micrometre in diameter to larger particles of 20 micrometres or more.

Some particles may be visible to the naked eye, such as large dust particles, but a microscope will enable the observation of smaller, inhalable particles. These fine particles, often with diameters of 2.5 micrometres or less, can pose significant health risks as they can reach deep into the lungs and even enter the bloodstream.

Additionally, mobile microscopy platforms, such as c-Air, offer a cost-effective and lightweight solution for air quality monitoring. These platforms utilise machine learning and computational microscopy to detect specific particles, providing accurate air quality data.

Discussing findings and causes

The petroleum jelly experiment is a simple yet effective way to teach students about air quality and pollution. It is a great introduction to the topic, especially for younger students, as it is easy to set up and does not require expensive equipment.

The experiment involves spreading a thin layer of petroleum jelly on glass slides, plastic plates, or graph paper. These are then placed in different locations, both inside and outside, for 24 hours. The jelly acts as a trap for particulate matter, and students can then observe and count the number of pollutants that have been caught.

When discussing the findings, students can compare the levels of pollution in different areas. For example, they may be surprised to find that certain indoor locations have higher pollution levels than expected. They can also discuss the differences between indoor and outdoor pollution and try to identify the sources of the pollutants.

The causes of air pollution can be varied, and this experiment can help students understand the impact of human activity. For instance, placing the slides or plates near a busy street or highway will likely result in a higher amount of particulate matter being trapped, indicating the negative impact of vehicle emissions. This can lead to a discussion about sustainable urban planning and the potential benefits of designs that reduce the need for cars, such as Frank Lloyd Wright's Broadacre City. Additionally, students can consider the health implications of air pollution and the importance of addressing it to improve overall air quality.

Frequently asked questions