Agriculture Reference
In-Depth Information
until the number of nanotoxicological research works began to increase exponen-
tially, mostly focused on human health (Royal Society
2004
). In relation to the
environmental impact, the number of studies is still small and does not reflect the
substantial number of new applications developed for these materials (Kahru and
Dubourguier
2010
).
In this context, ecotoxicology has gradually established itself as a multidis-
ciplinary field of research essential to elucidate the real impact of these new
materials in the environment.
13.3 Aquatic Nanoecotoxicology as a Major Data Source
Aquatic toxicity tests are widely used because these ecosystems are the main
enclosures of contaminants, whether coming from direct release into water bodies
through discharge of effluents or released into the air or deposited in soils (Kendall
et al.
2001
).
The aquatic environment is complex and diverse. It comprises several types of
ecosystems, among which are rivers, lakes, estuaries, seas, and oceans (Rang
et al.
1995
). They are open and dynamic systems capable of undergoing continuous
changes in their chemical composition. For example, in freshwater, calcium,
magnesium, and carbonate ions are the most abundant, but sodium, potassium,
phosphorus, iron, sulfur, and silicon compounds are also present. There are also
non-conserved components, which include dissolved O
2
,CO
2
, and N
2
gases;
nutrients such as phosphate and nitrate; dissolved organic compounds such as
amino acids and humic substances; trace elements such as copper, zinc, chromium,
molybdenum, vanadium, manganese, tin, iron, nickel, cobalt, and selenium; and
particulate materials such as sand, clay, colloid, nonliving tissues, and excreta
(Rang et al. 1995; Ravera
2004
).
Among the biochemical and physiological effects caused by toxic agents on
aquatic organisms, we can mention: change in cell membrane permeability; inter-
ference in adenosine 5
0
-triphosphate (ATP) production; reversible or irreversible
inhibition of enzymes; disturbances in carbohydrate metabolism; respiratory pro-
cess disorders by inhibiting electron transport and oxidative phosphorylation; lipid
metabolism disturbances, which may result in liver abnormalities; and change in
the structure or activity of enzymes that participate in regulatory processes, affect-
ing the synthesis and release of hormones (Costa et al.
2008
).
The toxicity tests can be classified into acute and chronic, depending on the
duration and final responses that are measured. The acute toxicity tests are used to
measure the effects of toxic agents on aquatic species during a short period of time
relative to the life of the test organism. They aim to estimate the dose or concen-
tration of a toxic agent that could produce a measurable response in a specific test
organism or population in a relatively short period of time, usually 24-96 h. The
toxic effects measured in acute toxicity tests include any response displayed by a
test organism or population resulting from a chemical stimulus. Typically, the
