Pesticides as Human Endocrine Disruptors
With all the PowerPoint presentations and discussion about the different types of pesticides and the analysis of the MSDS and labels, students should realize that they are dealing with things that can potentially have some lasting effects on them if handled improperly. Many of the chemicals that are used in the landscaping industry disrupt cellular development in order to impair living things at ultra-low, environmentally relevant concentrations. Clear scientific evidence indicates that humans are not immune from the effects of these chemicals. Endocrine disruptors put the welfare of our children at stake and make these chemicals a top priority of green chemistry efforts.
Endocrine disrupting chemicals are substances that can cause adverse effects by interfering in some way with the body's hormones or chemical messengers. Hormones play a crucial role in normal cell differentiation in early life stages, so exposure to endocrine disrupting substances in the egg or womb can alter the normal process of development. Mature organisms can be affected, but the developing organisms are especially vulnerable. Exposure at this early stage may not be evident until later in life, causing effects such as learning disability, behavior and reproduction problems, and increased susceptibility to cancer and other diseases.[17]
The effects of the endocrine disruptor are dependent upon which hormone system is targeted. They can either bind to the hormone's receptor and mimic the hormone, or block the action of the hormone. They can also stimulate or inhibit the enzymes responsible for the synthesis or clearance of the hormone, and, thereby, give rise to an increased or decreased action of the hormone. Landscape chemicals are identified in all of the categories! These chemicals include sex hormone disruptors, thyroid hormone disruptors and suppressors of the hormones released by the brain, and they have affects on steroid synthesis and metabolism.[17]
Wildlife is especially vulnerable to the endocrine disrupting effects of pesticides, because these chemicals are deliberately released into the environment. Effects linked to endocrine disruption have been found in invertebrates, reptiles, fish, birds, and mammals living in polluted areas. Humans are also exposed from residues on fruits and vegetables and from contaminated meat, fish, and dairy products due to the build up of persistent and bioaccumulating pesticides in the food chain.
To have students explore this concept, I will have them do a lesson on endocrine disruptors.[18] Through this two period lesson, they are introduced to the endocrine system and study what is known and not known about chemicals that disrupt this system in humans. This lesson introduces environmental surprises, scientific uncertainty, and social decision making in the context of the environmental change represented by endocrine disruptors.
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