Oxidative Potential of Ambient Aerosols:An Indian Perspective

Abstract

Keywords: Ambient aerosols, oxidative potential, reactive oxygen species, pollutants sources.AMBIENT aerosols are tiny particles suspended in the air with size predominantly ranging between 10 nm to 10 m. Aerosols consist of a wide variety of organic and inorganic chemical species such as major cations and anions, transition metals, heavy metals, elemental carbon (EC) and organic carbon species. They are injected into the atmosphere from a variety of natural (e.g. mineral dust, sea-salt, forest fire, volcanic eruption) and anthropogenic (e.g. biomass burning, fossil-fuel burning, vehicular and industrial emissions) sources, either directly (primary particles) or through the chemical processing of their gaseous precursors (secondary particles), or both. Aerosols are known to affect the earth's climate (radiation budget, hydrological cycle), aquatic ecosystem (biogeochemistry of oceans and lakes), and air quality (visibility and human health) 1 . Aerosols react with several atmospheric trace gases that leads to change in their chemical and physical properties, which can affect their optical and hygroscopic properties as well as bioavailability of nutrients. Although all the effects of aerosols are important, the effect on air quality is gaining specific interest and attention, as it directly relates to public health. There are numerous studies in the literature showing a direct relationship between high concentrations of ambient fine particles, and morbidity and mortality 2-6 . One of the widely proposed mechanisms related to the effect of aerosols on human health is that several types of aerosols produce reactive oxygen species (ROS) in situ in the human respiratory system, while breathing. Production of ROS causes imbalance between oxidants and antioxidants in the body and leads to several cardiopulmonary diseases like bronchitis, breathing problem, asthma, lung cancer, heart attack and even death 2-4 . ROS are oxygen-containing chemical species with strong oxidizing capability. Although molecular oxygen is not very reactive due to spin restriction in its outermost orbits, when paramagnetic centres (different aerosol species) react with O 2 , ROS are generated. They include families of oxygen-centred or related free radicals, ions and molecules. The free-radical family includes, but is not limited to, hydroxyl, hydroperoxyl and organic peroxy radicals, ions consist of superoxide, hypochlorite and peroxynitrite ions, and molecules are represented by hydrogen peroxide, organic and inorganic peroxides (Figure 1). These ROS can be exogenous (ROS are constituents of the particle) and/or endogenous (formed by in situ reactions where particles act as catalysts). Exogenous ROS are also called particle-bound ROS, whereas endogenous ROS are called particle-induced ROS. Here, it is important to note that ambient particles act as a catalyst for the generation of endogenous ROS and therefore, they can be active until they are removed from the place of generation (atmosphere, human respiratory system, plants). Reactivity of ...

Real-Time Measurements of PM2.5 Oxidative Potential Using a Dithiothreitol Assay in Delhi, India

“…The overall toxicity of PM 2.5 is dependent on both its mass concentration and the composition. , Previous studies conducted in the Indo-Gangetic Plains have indicated that PM 2.5 in Delhi is a mixture of particles (or their precursors) emitted from various emission sources, including postharvest crop burning, vehicles, industry, waste burning, and construction activities. − These mixtures of various chemical species (e.g., organic compounds, inorganic ions, transition metals, etc.) coming from different sources are expected to be highly toxic, , but data about the toxicological properties of PM 2.5 in the Indian subcontinent are currently lacking. , …”

“…coming from different sources are expected to be highly toxic, 14,15 but data about the toxicological properties of PM 2.5 in the Indian subcontinent are currently lacking. 16,17 The oxidative potential (OP) of PM, i.e., the ability of particles to generate reactive oxygen species (ROS) or consume antioxidants, is an intrinsic property and has recently gained popularity as a potential health metric to estimate the PM toxicity. 18−22 The OP of PM can be measured by different chemical and biological assays.…”

Chemical Composition and Oxidative Potential of Atmospheric PM10 over the Arabian Sea

“…Such processes can also alter the aerosol OP and thus their effects on surface ocean biogeochemistry. Information on aerosol OP over the Indian subcontinent is lacking because of a lack of studies . No studies worldwide, to the best of our knowledge, have reported the OP of ambient aerosol over marine environments.…”

“…Information on aerosol OP over the Indian subcontinent is lacking because of a lack of studies. 19 No studies worldwide, to the best of our knowledge, have reported the OP of ambient aerosol over marine environments.…”

Aerosol-type classification based on AERONET version 3 data over two megacities of Pakistan

“…To reduce such uncertainties, based on their chemical and physical properties, it is necessary to study the different types of aerosols on the ground and in space as well (Eck et al, 1999;Dubovik et al, 2002;Satheesh, 2005). Besides these effects, aerosols study is also important in terms of prompting poor air quality (Kumar et al, 2017), poor visibility (Hanet et al, 2012), and regulation of oxidative properties of the atmosphere (Patel., 2017), which adverse effects on human's health.…”