Case study 3

Question

Botswana may struggle to now meet WHO pollution standards
Botswana might struggle to meet the new World Health Organisation (WHO) air quality
guidelines following an announcement by the health agency that harms from air pollution
begin at much lower levels than previously thought. A year ago, the State of Global Air
2020 Report highlighted that Botswana is polluted twice beyond the threshold limit. The
report noted that Botswana has high concentration of deadly particle pollution, recording the
concentration of poisonous PM2.5 particles at two and half times over the WHO threshold
limit. The 2020 report also noted that Botswana has high exposure to particle matter
concentration at 25 micrograms per cubic metre which is above WHO’s Air Quality
Guideline for PM2.5 of only 10 micrograms per cubic metre.
The health agency notes that since 2005, more evidence has emerged which shows that air
pollution affects health at lower concentrations than previously understood. “WHO has
adjusted almost all the air quality guideline levels downwards, warning that exceeding the
new levels are associated with significant risks to health,” the health agency said in a
statement. Furthermore, the health agency lowered acceptable thresholds for several
pollutants, including ultrafine PM2.5 particles that Botswana has had a difficult time trying
to contain.
WHO says the major components of particle matter are sulphate, nitrates, ammonia, sodium
chloride, black carbon, mineral dust and water; and are mainly emitted by coal-burning
power plants, industrial activity, vehicle emissions, waste burning, and other human
activities.
The new WHO pollution guidelines which aim to protect people from the adverse effects of
air pollution and are used by governments as a reference for legally binding standards. It is
not immediately clear how this will affect policy in Botswana as the country announced a
few months ago that they are ramping up the use of coal to reduce over dependence on
diamonds.
Question 3 [20 MARKS]
In the passage above, it was said that Botswana fails to meet the required pollutants
standard, as a result the air is not fully free from pollutants. Having studied OHS through
BOU, what are the physical factors that may affect ventilation, Discuss?

Answer 1

Ventilation in any given environment, including workplaces, is essential for maintaining air quality and ensuring that indoor air is free from pollutants. The inability of Botswana to meet air quality standards, as highlighted in the WHO guidelines, emphasizes the importance of addressing ventilation, especially in polluted areas. Several physical factors can significantly impact ventilation, particularly in improving air quality when external conditions are poor. Here are some of the key physical factors that may affect ventilation:

1. Building Design and Structure

• Layout: The arrangement of rooms, open spaces, and airflow paths within a building directly influences how air circulates. Narrow hallways and closed-off spaces can limit airflow.
• Ceiling Heights: Higher ceilings may allow for better air mixing, reducing the concentration of pollutants near the floor level. Conversely, low ceilings can trap warm air and contaminants.
• Windows and Openings: The number, size, and position of windows and other openings determine how much outdoor air can enter a space. Properly placed windows can enhance natural ventilation.

2. Airflow Dynamics

• Pressure Differences: Natural ventilation relies on differences in air pressure inside and outside a building. Positive and negative pressures can either promote or obstruct airflow, depending on environmental conditions (e.g., wind speed and direction).
• Stack Effect: The natural rise of warm air can create an upward draft in buildings, encouraging fresh air to enter from lower openings. Buildings with multiple stories can see this effect more prominently.

3. Environmental Conditions

• Temperature: The external temperature can affect the density and movement of air. Warm air tends to rise, while cold air sinks, influencing how air moves through spaces.
• Humidity: High humidity levels can contribute to condensation and mold growth, which can affect air quality. In climates with varying humidity, ventilation systems need to be designed to handle moisture properly.
• Outdoor Air Quality: Existing outdoor air pollution levels can directly impact indoor air quality. In areas like Botswana, where PM2.5 concentrations are high, introducing outdoor air might exacerbate indoor pollution levels.

4. Ventilation Systems

• Type of System Used: Mechanical ventilation (HVAC systems) can provide controlled airflow, regardless of external conditions. The choice between natural and mechanical systems affects how air is exchanged within a building.
• Efficiency and Maintenance: The performance and maintenance of ventilation systems are crucial. Filters need to be regularly changed and systems checked to ensure effective operation, as inefficient systems can recirculate pollutants.

5. Obstructions and Barriers

• Furniture and Equipment: The placement of furniture and equipment can block airflow pathways, leading to stagnant air and poor ventilation in certain areas.
• Duct Design: In mechanical ventilation systems, the design and size of ducts can affect how well air moves through a building. Restrictions can cause uneven distribution of air and localized areas of high or poor air quality.

6. Insulation and Sealing

• Insulation Levels: Improper insulation can lead to air leaks, which can significantly reduce the effectiveness of ventilation systems. Buildings that are not well-sealed may suffer from drafts that can bring in outdoor pollutants.
• Sealing Cracks and Gaps: Identifying and sealing gaps in walls, windows, and doors can maintain controlled indoor environments by preventing unwanted outdoor air intrusion.

Conclusion

Improving ventilation is crucial for managing air quality, especially in areas affected by pollution. In Botswana's context, addressing these physical factors can create a healthier indoor environment and help mitigate some of the effects of outdoor air pollution. As air quality regulations evolve, it will be imperative for policymakers and building designers to take these aspects into account to enhance the overall ventilation systems in residential, commercial, and industrial settings.