Pesticide Residues in Man - Pesticides: Evaluation of Environmental Pollution - page 503

EDCs has been confirmed (Amaral Mendes 2002; Charlier and Plomteux 2002). In
addition to most OCPs, other pesticides, such as organophosphates, carbamates,
triazines, and pyrethroids, that are less persistent and less toxic than the OCs were
used to replace them, but many are now confirmed or suspected EDCs (Andersen
et al. 2002).
viii. Cytogenetic effects : Cytogenetic damage related to pesticide exposure has been
reported in various populations. Some investigators (e.g., De Ferrari et al. 1991;
Kourakis et al. 1992; Joksic et al. 1997) have reported significant differences in
the percentage of chromosomal aberrations (CAs) in exposed individuals (range,
2.66%-10.30%) compared with the control (range, 0.53%-5.52%). In workers of flower
plantations located at Quito, Ecuador, South America, exposed to 27 pesticides
(e.g., aldicarb, benomyl, captan, carbendazim, carbofuran, cartap, chlorothalonil,
cypermethrin, deltamethrin, endosulfan, fenamiphos, fosetyl, iprodione, profeno-
fos, propineb, vinclozolin, etc.), CA showed an increased frequency compared with
the control group (20.59% vs. 2.73%; p < 0.001). Levels of erythrocyte AChE below
the optimal level (>28 U/mL blood) were found in 88% of the exposed individuals
(Mino et al. 2002).
ix. Immunotoxicity : The scientific evidence suggesting that many pesticides damage
the immune system is impressive. Animal studies have found that pesticides
alter the immune system's normal structure, disturb the immune responses, and
reduce the animal's resistance to antigens and infectious agents. There is con-
vincing direct and indirect evidence that these findings carry over to the human
populations exposed to pesticides (WRI 1996). All mammalian (and avian and
fish) immune systems are structurally similar, and considerable evidence shows
that animal models are valid for testing human immunotoxicity (Turner 1994).
Hundreds of studies (including compounds from different classes) have shown
that pesticides can induce changes in the immune system structure and function,
and these changes correlate closely in experimental animals with altered host
resistance to pathogens (Vos et al. 1994). Malathion, which is considered a com-
pound with very low toxicity (oral LD50 = 2100 mg/kg body weight), for example,
dysregulates the immune system, especially affecting the nonspecific immune
mechanisms. Chronic exposure at low doses over prolonged periods can also
depress the humeral immune responses (Barnett and Rogers 1994). In addition to
the active ingredients, pesticide solvents, inert materials, impurities, and contami-
nants cause measurable immunosuppression in several species (Kerkvliet 1994).
x. Cancer and immunosuppression : Studies have shown that pesticide exposure signifi-
cantly reduces resistance to bacterial, viral, and parasitic infections and promotes
tumor growth in many animal species (Bradley 1995). People exposed to pesti-
cides are at an increased risk of contracting certain cancers known to be associated
with immune suppression (Blair et al. 1992). Studies that specifically focused on
pesticide exposure (occupationally and nonoccupationally) have found that phe-
noxy acid herbicides and other pesticides are associated with NHL and soft tissue
sarcoma—two cancers associated with immunosuppression—and also with leu-
kemia, multiple myeloma, and brain cancer (Leiss and Savity 1995). The fact that
the farmers and others exposed to pesticides experience higher risks for the same
cancers that afflict patients with clear immune deficiencies suggests that pesti-
cides suppress the immune system and its self-regulating capabilities and thus
raise cancer risks (WRI 1996).