different types of stress (Benhamou 1996; Tierranegra-García et al. 2011; Zia
et al. 2017). However, the role of these elicitor molecules toward metal foliar
uptake, toxicity, and detoxification is not yet well-established. Therefore, studies
may be performed to evaluate the effect of different elicitors toward foliar metal
uptake, its toxicity, and detoxification.
9 Summary
This review highlighted the fate and behavior of metal-PM in the ecosystems as well
as their associated health risks. Metal-PM is emitted to the atmosphere by various
natural and anthropogenic activities, the latter being the major source. During their
processing in factories, different chemical forms of heavy metal(loid)s may attach to
PM of varying sizes. The chemical form of a metal and the size of PM depend on the
source. The concentration of metal-PM in the atmosphere may vary among different
areas such as urban, rural, and industrial areas. In industrial areas, the concentration
of metal-PM in the atmosphere may reach up to several folds higher than the
permissible levels set by WHO as reported in various countries of Europe, Asia,
and America.
After release into the atmosphere, metal-PM can travel over a long distance
depending on their composition and size, in addition to meteorological and climatic
factors. Transport of metal-PM varies on a temporal and spatial scale. Atmospheric
metal-PM finally deposit to terrestrial ecosystems such as soil, water, buildings, and
plant canopy. In this way, these metal-PMs contaminate different parts of the
ecosystem by heavy metals.
In soil, metal-PM becomes the part of soil depending on the nature of soil or is
being uptake by plants. Heavy metal(loid)s deposited from the atmospheric are
considered relatively more available for plant uptake compared to those present/
adsorbed in the soil.
Deposition of metal-PM on aerial plant parts is considered an important source
of plant contamination. Although rarely discussed and explained, foliar heavy
metal(loid) deposition and uptake can be a major source of heavy metal(loid)
accumulation in plants (shoots). In addition, metal-PM can be inhaled directly by
humans and get deposited in different organs inside the body. After inhalation,
metal-PM can induce several toxic effects to humans. At cellular level, heavy
metal(loid)s can overproduce reactive oxygen species inside the human body, thus
leading to oxidative stress and toxicity to various micro- and macromolecules.
Conflict of Interest On behalf of all authors, the corresponding author states that there is no
conflict of interest.
98
M. Shahid et al.
et al. 2017). However, the role of these elicitor molecules toward metal foliar
uptake, toxicity, and detoxification is not yet well-established. Therefore, studies
may be performed to evaluate the effect of different elicitors toward foliar metal
uptake, its toxicity, and detoxification.
9 Summary
This review highlighted the fate and behavior of metal-PM in the ecosystems as well
as their associated health risks. Metal-PM is emitted to the atmosphere by various
natural and anthropogenic activities, the latter being the major source. During their
processing in factories, different chemical forms of heavy metal(loid)s may attach to
PM of varying sizes. The chemical form of a metal and the size of PM depend on the
source. The concentration of metal-PM in the atmosphere may vary among different
areas such as urban, rural, and industrial areas. In industrial areas, the concentration
of metal-PM in the atmosphere may reach up to several folds higher than the
permissible levels set by WHO as reported in various countries of Europe, Asia,
and America.
After release into the atmosphere, metal-PM can travel over a long distance
depending on their composition and size, in addition to meteorological and climatic
factors. Transport of metal-PM varies on a temporal and spatial scale. Atmospheric
metal-PM finally deposit to terrestrial ecosystems such as soil, water, buildings, and
plant canopy. In this way, these metal-PMs contaminate different parts of the
ecosystem by heavy metals.
In soil, metal-PM becomes the part of soil depending on the nature of soil or is
being uptake by plants. Heavy metal(loid)s deposited from the atmospheric are
considered relatively more available for plant uptake compared to those present/
adsorbed in the soil.
Deposition of metal-PM on aerial plant parts is considered an important source
of plant contamination. Although rarely discussed and explained, foliar heavy
metal(loid) deposition and uptake can be a major source of heavy metal(loid)
accumulation in plants (shoots). In addition, metal-PM can be inhaled directly by
humans and get deposited in different organs inside the body. After inhalation,
metal-PM can induce several toxic effects to humans. At cellular level, heavy
metal(loid)s can overproduce reactive oxygen species inside the human body, thus
leading to oxidative stress and toxicity to various micro- and macromolecules.
Conflict of Interest On behalf of all authors, the corresponding author states that there is no
conflict of interest.
98
M. Shahid et al.