Indoor Air Cartoon Journal, May 2019, Volume 2, #60

Humans are surrounded by particles – liquid droplets and solids matter – both in the indoor and outdoor environment. Exposure to these particles occurs on surfaces or in the air (aerosols). The vulnerability in the indoor environment is of particular importance because of the higher surface to volume ratio. Additionally, the enclosed nature of the indoor environment potentially increases exposure.

There are several sources of human activities, building materials, and natural phenomenon contributing to the concentration of the particles. The source of a particle and mode of generation – mechanical or molecular – will determine the size of the particle and where it is deposited in the human body. The location particle deposit contributes to adverse health implications. The source of a particle adds to the nature of the particle toxicity. Particles may be contaminated biologically or chemically.

A large number of fine particles – those less than 2.5µm (PM2.5) – and ultrafine particle/nanoparticles – those less than 0.1µm (PM0.1) – can penetrate deep into the pulmonary region of the respiratory system. The airways and alveolar region have defense systems that protect the lungs. However, high concentrations of toxic particles could render these defense systems ineffective and expose the lungs to the toxic particles. A high concentration of the toxic particles will stimulate a high amount of inflammation in the lungs, potentially leading to pulmonary diseases such as asthma, bronchitis, chronic obstructive pulmonary diseases (COPD), lung cancer, etc. Thus, it is essential to reduce human exposure, especially those with a prior respiratory health problem, to particles as much as possible. The reduction should be a continuous effort.

Do you want to know more about this topic? Read Byrne and Baugh (2008), Donaldson and Tran (2002), and Nemmar et al. (2003) papers.