| − | Environmental chemicals, specifically sex steroids such as [[xenoestrogens]] and [[xenoandrogens]], cause effects on the brain's gender preference and can result in homosexuality in nature.<ref name=hines>{{cite journal |last=Hines |first=Melissa |last2= |first2= |date=2011-02-17 |title=Prenatal endocrine influences on sexual orientation and on sexually differentiated childhood behavior |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3296090/ |journal=Frontiers in Neuroendocrinology |volume=32 |issue=2 |pages=170-182 |doi=10.1016/j.yfrne.2011.02.006 |pmid=21333673}}</ref> Xenoestrogens and xenoandrogens alter the brain's [[sexual differentiation]] in a number of species, including rams, ferrets, zebra finches<ref>{{cite journal |last=Roselli |first=C.E. |last2=Stormshak |first2=F. |date=2009 |title=Prenatal Programming of Sexual Partner Preference |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2668810/ |journal=J. Neuroendocrinol |volume=21 |issue=4 |pages=359-364 |doi=10.1111/j.1365-2826.2009.01828.x |pmid=19207819}}</ref>, gulls, primates, and rodents, resulting in the masculinization of female brains/behavior (e.g. 'lesbian gulls') and feminization of male brains/behavior. Due to concern over environmental health risks [[endocrine disruption]] was the primary theme of the 27th International Neurotoxicology Conference.<ref name=intersect>{{cite journal |last=Weiss |first=Bernard |last2= |first2= |date=2013-12-01 |title=The Intersection of Neurotoxicology and Endocrine Disruption |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3458140/ |journal=Neurotoxicology |volume=33 |issue=6 |pages=1410-1419 |doi=10.1016/j.neuro.2012.05.014 |pmid=22659293}}<br>{{cite journal |last=He |first=Zhen |last2=Ferguson |first2=Sherry Ann |last3=Cui |first3=Li |last4=Greenfield |first4=Lazar John |last5=Paul3 |first5=Merle Gale |date=2013-10-15 |title=Development of the sexually dimorphic nucleus of the preoptic area and the influence of estrogen-like compounds |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4145994/ |journal=Neural Regen Res |volume=8 |issue=29 |pages=2763–2774 |doi= |pmid=25206587}}<br>{{cite journal |last=Svechnikov |first=Konstantin |last2=Stukenborg |first2=Jan-Bernd |last3=Savchuck |first3=Iuliia |last4=Söder |first4=Olle |date=2014 |title=Similar causes of various reproductive disorders in early life |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901882/ |journal=Asian Journal of Andrology |volume=16 |issue=1 |pages=50-59 |doi=10.4103/1008-682X.122199 |pmid=24369133 }}</ref> | + | Environmental chemicals, specifically sex steroids such as [[xenoestrogens]] and [[xenoandrogens]], change the brain's gender preference resulting in homosexuality in nature. According to Melissa Hines, "This article reviews the evidence regarding prenatal influences of gonadal steroids on human sexual orientation, as well as sex-typed childhood behaviors that predict subsequent sexual orientation. The evidence supports a role for prenatal testosterone exposure in the development of sex-typed interests in childhood, as well as in sexual orientation in later life, at least for some individuals... The empirical record generally supports this model for a wide range of brain regions and behaviors that differ on the average for male and female animals. For example, treating female rodents with testosterone early in life decreases their female-typical behavior in adulthood, and increases their male-typical behavior."<ref name=hines>{{cite journal |last=Hines |first=Melissa |last2= |first2= |date=2011-02-17 |title=Prenatal endocrine influences on sexual orientation and on sexually differentiated childhood behavior |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3296090/ |journal=Frontiers in Neuroendocrinology |volume=32 |issue=2 |pages=170-182 |doi=10.1016/j.yfrne.2011.02.006 |pmid=21333673}}</ref> |
| | + | These chemicals are produced in quantities of billions of kg. per year, and are used prominently in cosmetics and pesticides such as [[diethylstilbestrol]] (DES) and [[DDT]] while appearing also in food and dust particles. When in the form of [[Phthalate|phthalates]] they can be widely used in plastics including children's toys, food and drink containers, and medical devices.<ref name=intersect>{{cite journal |last=Weiss |first=Bernard |last2= |first2= |date=2013-12-01 |title=The Intersection of Neurotoxicology and Endocrine Disruption |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3458140/ |journal=Neurotoxicology |volume=33 |issue=6 |pages=1410-1419 |doi=10.1016/j.neuro.2012.05.014 |pmid=22659293}}</ref><ref>{{cite journal |last=He |first=Zhen |last2=Ferguson |first2=Sherry Ann |last3=Cui |first3=Li |last4=Greenfield |first4=Lazar John |last5=Paul3 |first5=Merle Gale |date=2013-10-15 |title=Development of the sexually dimorphic nucleus of the preoptic area and the influence of estrogen-like compounds |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4145994/ |journal=Neural Regen Res. |volume=8 |issue=29 |pages=2763–2774 |doi= |pmid=25206587}}</ref><ref>{{cite journal |last=Svechnikov |first=Konstantin |last2=Stukenborg |first2=Jan-Bernd |last3=Savchuck |first3=Iuliia |last4=Söder |first4=Olle |date=2014 |title=Similar causes of various reproductive disorders in early life |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3901882/ |journal=Asian Journal of Andrology |volume=16 |issue=1 |pages=50-59 |doi=10.4103/1008-682X.122199 |pmid=24369133 }}</ref> Xenoestrogens and xenoandrogens alter the brain's [[sexual differentiation]] in a number of species, including rams, ferrets, zebra finches<ref>{{cite journal |last=Roselli |first=C.E. |last2=Stormshak |first2=F. |date=2009 |title=Prenatal Programming of Sexual Partner Preference |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2668810/ |journal=J. Neuroendocrinol |volume=21 |issue=4 |pages=359-364 |doi=10.1111/j.1365-2826.2009.01828.x |pmid=19207819}}</ref>, gulls, primates<ref name=intersect/>, and rodents<ref>{{cite journal |last=Matsuda |first=Ken Ichi |last2= |first2= |date=2014-10-28 |title=Epigenetic changes in the estrogen receptor α gene promoter: implications in sociosexual behaviors |url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4211403/ |journal=Front Neurosci |volume=8 |issue=344 |pages= |doi=10.3389/fnins.2014.00344 |pmid=25389384}}</ref>, resulting in the masculinization of female brains/behavior (e.g. 'lesbian gulls') and feminization of male brains/behavior.<ref name=intersect/> |
| | + | According to Bernard Weiss, "disagreements arise partly from arguments about the roots of homosexuality, and about questions of gender identity and others that at one time would have seemed quite remote from neurotoxicology." Due to concern over environmental health risks including cancer, thinning of bald eagle eggshells, and reduced species reproduction, [[endocrine disruption]] was the primary theme of the 27th International Neurotoxicology Conference.<ref name=intersect/> |