• The attachment of heavy metal(loid)s to PM occurs during their release from the
source (primary metal-PM), or they may get attached to PM in the atmosphere
after their release (secondary metal-PM). The interaction or the type of binding
between heavy metal(loid)s and PM (primary and secondary metal-PM) has not
yet been described in the literature. Moreover, the type of industrial processes,
source of energy used in these processes, as well as the meteorological factors
may also affect the interaction between heavy metal(loid)s and PM and thereby
their composition, speciation, and associated health risks. Attention may, therefore, be given to these factors and interactions of metals and PM.
• The long-distance travel, as well as the deposition and fate (adsorption/desorption
in the soil, uptake by plants, and deposition in lungs) of metal-PM in the
environment, is associated with composition and the size of metal-PM, meteorological conditions, physicochemical properties of soil/phyllosphere. Therefore,
the temporal and spatial distributions, as well as the effects of different factors,
need to be studied in detail.
• Total heavy metal(loid) or metal-PM concentrations in the environment (air, soil,
water) are commonly used as the main criteria for assessing the pollution conditions and associated hazards. However, recent data show that the biogeochemical
behavior of metals in the environment is mainly governed by their chemical
speciation. The scarcity of data about metal speciation in the industrially emitted
PM is mainly due to the lack of analytical tools, both sensitive and specific to the
size of the particles. Therefore, more attention is required to establish tools to
assess chemical speciation of metal-PM as well as the relationship of chemical
speciation of heavy metal(loid)s in PM with their biogeochemical behavior in the
atmosphere-soil-plant-human system.
• Some studies also highlight that comparatively less attention is given to metalPM emitted from the industries compared to traffic emissions (urban areas). The
chemical speciation, composition, and the biogeochemical behavior of metal-PM
emitted from different sources (industry, automobiles, mining, etc.) may vary
greatly. Therefore, metal-PM emitted from different sources and the associated
health risks may be categorized accordingly.
• Contrary to European countries where human health is nowadays protected
thanks to European Commission Regulation (EC) No. 221/2002 and REACH
regulation (EU n
1907/2006) promoting a more secure use and release of chemical substances in the atmosphere/environment, the less developed countries such
as subcontinent need to reinforce the global information and the restrictions for
(eco)toxic chemical substance release into the atmosphere in order to avoid and
reduce human exposure and sanitary impacts. Moreover, on the global scale,
available socio-scientific publications illustrate that ecological transitions are
necessary in various sectors in order to preserve human and environmental/
atmospheric health.
• There is also limited data regarding metal-PM uptake by vegetables and crops,
accumulation in edible plant parts, and the associated human health hazards.
Moreover, elicitor molecules such as silicon, salicylic acid, and methyl salicylate
have been well-reported to affect plant growth and defense mechanisms under
Ecotoxicology of Heavy Metal(loid)-Enriched Particulate Matter: Foliar. . .
97
source (primary metal-PM), or they may get attached to PM in the atmosphere
after their release (secondary metal-PM). The interaction or the type of binding
between heavy metal(loid)s and PM (primary and secondary metal-PM) has not
yet been described in the literature. Moreover, the type of industrial processes,
source of energy used in these processes, as well as the meteorological factors
may also affect the interaction between heavy metal(loid)s and PM and thereby
their composition, speciation, and associated health risks. Attention may, therefore, be given to these factors and interactions of metals and PM.
• The long-distance travel, as well as the deposition and fate (adsorption/desorption
in the soil, uptake by plants, and deposition in lungs) of metal-PM in the
environment, is associated with composition and the size of metal-PM, meteorological conditions, physicochemical properties of soil/phyllosphere. Therefore,
the temporal and spatial distributions, as well as the effects of different factors,
need to be studied in detail.
• Total heavy metal(loid) or metal-PM concentrations in the environment (air, soil,
water) are commonly used as the main criteria for assessing the pollution conditions and associated hazards. However, recent data show that the biogeochemical
behavior of metals in the environment is mainly governed by their chemical
speciation. The scarcity of data about metal speciation in the industrially emitted
PM is mainly due to the lack of analytical tools, both sensitive and specific to the
size of the particles. Therefore, more attention is required to establish tools to
assess chemical speciation of metal-PM as well as the relationship of chemical
speciation of heavy metal(loid)s in PM with their biogeochemical behavior in the
atmosphere-soil-plant-human system.
• Some studies also highlight that comparatively less attention is given to metalPM emitted from the industries compared to traffic emissions (urban areas). The
chemical speciation, composition, and the biogeochemical behavior of metal-PM
emitted from different sources (industry, automobiles, mining, etc.) may vary
greatly. Therefore, metal-PM emitted from different sources and the associated
health risks may be categorized accordingly.
• Contrary to European countries where human health is nowadays protected
thanks to European Commission Regulation (EC) No. 221/2002 and REACH
regulation (EU n
1907/2006) promoting a more secure use and release of chemical substances in the atmosphere/environment, the less developed countries such
as subcontinent need to reinforce the global information and the restrictions for
(eco)toxic chemical substance release into the atmosphere in order to avoid and
reduce human exposure and sanitary impacts. Moreover, on the global scale,
available socio-scientific publications illustrate that ecological transitions are
necessary in various sectors in order to preserve human and environmental/
atmospheric health.
• There is also limited data regarding metal-PM uptake by vegetables and crops,
accumulation in edible plant parts, and the associated human health hazards.
Moreover, elicitor molecules such as silicon, salicylic acid, and methyl salicylate
have been well-reported to affect plant growth and defense mechanisms under
Ecotoxicology of Heavy Metal(loid)-Enriched Particulate Matter: Foliar. . .
97