Endocrine DisruptionEndocrine Disruption
Faith M. OiUniversity of Florida
Entomology and Nematology Dept.Gainesville, FL 32611
The Concerns
• Endocrine disrupting chemicals (EDCs) have been implicated in everything from alligator feminization to human infertility, cancer and recently obesity.
• EPA is beginning Tier 1 screening– Tier 2 concentrates on doses
• Documentation has been and will continue to be difficult and controversial
EDC Brief History
• 1930’s, observations that synthetic chemicals could mimic hormones
• 1991, Wingspread– “Chemically induced alternations in sexual
development: The wildlife/human connection”
EDC Brief History
• “Many compounds introduced into the environment by human activity are capable of disrupting the endocrine system of animals, including fish, wildlife, and humans. Endocrine disruption can be profound because of the crucial role hormones play in controlling development.”
The Endocrine Disruption Screening Program
Investigations into the Effects of EDCs
• Sperm quality—several studies report decline• Fertility—implication, exposure to high levels can
impair fertility and increase rate of miscarriage• Abnormalities in male sex organs• Precocious puberty• Association with certain cancers
– Testicular cancer increase from 1973 to 1999 across all age groups
• Caucasian: 51.8%• African-American: 49.4%
– Breast cancer increase • Caucasian: 27.9% • African-American: 34.8%
– Brain cancer increase in children 14 or younger• 50.2%
Routes of Exposure
• Oral-- ingestion
• Dermal-- skin contamination (60-90%)
• Inhalation-- breath airborne insecticides (<1%)
• Ocular-- eyes
Acute Toxicity• Definition: Ability of a chemical to do
systemic damage resulting from a single exposure to a relatively large dose
• Effects are usually seen within minutes to hours of exposure
How Does the LD50 Work?The Concept
• Acute toxicity is measured by the LD50
– LD50 (Lethal Dose): Dose that it takes to kill 50% of the test population
Who invented the concept of the Who invented the concept of the LD50? J. W. Trevan, 1927. Was LD50? J. W. Trevan, 1927. Was trying to estimate relative poisoning trying to estimate relative poisoning effects of drugs and medicines.effects of drugs and medicines.
http://web.bryant.edu/~dlm1/sc372/readings/toxicology/endocrinedisrupter.jpg
•Some chemicals mimic a natural hormone, fooling the body into over-responding to the stimulus (e.g., a growth hormone that results in increased muscle mass), or responding at inappropriate times (e.g., producing insulin when it is not needed).•block the effects of a hormone from certain receptors (e.g. growth hormones required for normal development).•directly stimulate or inhibit the endocrine system and cause overproduction or underproduction of hormones•Epa.gov
http://www.niehs.nih.gov/health/topics/agents/endocrine/images/plastics.jpg
http://www.scientificamerican.com/media/inline/new-website-maps-endocrine-disruptors_1.jpg
Endocrine DisruptionThe Reader’s Digest Version
• Endocrine system secretes hormones into the blood stream and works in conjunction with the nervous system
• EDCs mimic hormones and interfere with synthesis, secretion, transport, binding, action or elimination of natural hormones.
• EDCs are bad for adults, worse for children and worst for unborn children of parents who are exposed
Endocrine DisruptionThe Reader’s Digest Version
• Hypothalamus - The hypothalamus links our endocrine and nervous systems together. The hypothalamus drives the endocrine system.
• Pituitary gland - The pituitary gland receives signals from the hypothalamus. The posterior lobe secretes hormones that are made by the hypothalamus. The anterior lobe produces its own hormones, several of which act on other endocrine glands.
Endocrine DisruptionThe Reader’s Digest Version
• Pancreas - The pancreas is responsible for producing glucagon and insulin. Both hormones help regulate the concentration of glucose (sugar) in the blood.
• Gonads - produce steroids that affect growth and development and also regulate reproductive cycles and behaviors. The major categories of gonadal steroids are androgens, estrogens, and progestins, all of which are found in both males and females but at different levels.
Endocrine DisruptionThe Reader’s Digest Version
• Children are not little adults– Pound for pound, a
child’s exposure is greater than an adults (dose-response)
– Immature blood-brain barrier—allows more chemical passage
– Detoxication systems may not be fully functional—timing of exposure.
Endocrine DisruptionThe Reader’s Digest Version
• “Because children have more future years of life than most adults, they have more time to develop chronic diseases that may be triggered by early exposures.”
• Landrigan et al. 2003. Assessing the effects of endocrine disruptors in the national children’s study. Environ. Health Perspectives 111(13): 1678-1682.
Solution?
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