Gerald A. LeBlanc | |
---|---|
Nationality | American |
Occupation(s) | Biologist, toxicologist, author, and academic |
Academic background | |
Education | BS in Biology MA in Biology PhD in Biology |
Alma mater | University of Massachusetts Dartmouth Bridgewater State University University of South Florida |
Thesis | Glutathione S-Transferases of Daphnia magna: Characterization of Structure and Function (1986) |
Academic work | |
Institutions | North Carolina State University |
Gerald A. LeBlanc is an American biologist,toxicologist,author,and academic. He is a Professor Emeritus in the Department of Biological Sciences at the North Carolina State University. [1]
LeBlanc's research interests span the fields of environmental toxicology and risk assessment with a focus on investigating the processes involved in the endocrine regulation of reproduction and development,as well as how environmental agents can disrupt these processes. He is the author of the book,Everyday Chemicals:Understanding the Risks and has published over 190 articles. [1]
LeBlanc received his bachelor's degree in biology from the University of Massachusetts Dartmouth in 1975,followed by a Master's in Biology from Bridgewater State University in 1981. Following his Bachelor's,he started his professional career as an Aquatic Toxicologist at EG&G Bionomics in Wareham,Massachusetts in 1975,a position he held for five years. Subsequently,in 1980,he was appointed as the Director of Toxicology and held that position until 1983. He then joined the University of South Florida in Tampa in 1983 as a Research Associate and received his Ph.D. in biology in 1986. From 1986 to 1989 he served as a Research Fellow in the Department of Biological Chemistry &Molecular Pharmacology and Dana-Farber Cancer Institute at Harvard Medical School where he completed his post-doctoral training. [2]
LeBlanc began his academic career in 1989 at North Carolina State University,where he became a professor of Toxicology and Environmental Health. He also served as an adjunct professor from 2012 to 2016 in the Department of Biological Sciences at Clemson University in South Carolina. [3]
LeBlanc is most known for his contributions to the field of environmental health sciences,focusing his research on the effects of environmental contaminants on human and environmental health. With a particular emphasis on endocrine-disrupting compounds,his research has centered on exploring the mechanisms of action and toxicological properties of diverse environmental chemicals. In his book,Everyday Chemicals:Understanding the Risks,he has provided details into the potential health risks associated with chemicals to which people are commonly exposed and has given a nontechnical overview of the essential factors involved in assessing whether exposure to chemicals in everyday lives could cause harm. [4]
LeBlanc's research in the field of toxicology,particularly centered on endocrine disruption,has contributed to the understanding of the impact of environmental contaminants on human [5] and wildlife health. [6] He investigated the impacts of endocrine-disrupting chemicals on mammals, [7] fishes, [8] reptiles, [9] and invertebrates. [10] He identified the suite of nuclear receptors in the crustacean,Daphnia pulex, [11] and functionally characterized several of these receptors. [12] He deciphered the neuro-endocrine signaling pathway responsible for sex determination in some crustaceans, [13] including the discovery of the hormone responsible for sex determination,methyl farnesoate, [14] and its receptor protein. [15] He also demonstrated that some insecticides can mimic the action of methyl farnesoate in daphnids resulting in altered sex ratios of offspring. [16]
In 2005,LeBlanc created a mathematical model that integrated concentration addition,response addition,and toxicokinetic interactions to enable the assessment of the toxicity of chemical mixtures. [17] He demonstrated the utility of this model by assessing the joint toxicity of 9 chemicals commonly found in surface waters in the US. [18] This model has been used by regulatory agencies [19] and has been recommended by the National Research Council in the assessment of risks to endangered and threatened species from exposure to pesticide mixtures. [20]
LeBlanc has conducted research in risk assessments,notably,identifying chemicals for prioritization in environmental risk assessments. [21] He suggested the integration of surrogate species and biomarkers of chronic toxicity into conventional toxicity assessments to enhance the accuracy and effectiveness of environmental risk assessments. [22] In a collaborative study,he suggested that hepatic testosterone biotransformation enzymes serve as more reliable indicators of puberty compared to preputial separation,and recommended the inclusion of these enzymes in risk assessment protocols for potential xenoestrogens. [23] He assessed the risk associated with several environmental chemicals including phthalate esters in bottled drinking water [24] and tributyltin in marine organisms. [25]
Piperonyl butoxide (PBO) is a pale yellow to light brown liquid organic compound used as an adjuvant component of pesticide formulations for synergy. That is,despite having no pesticidal activity of its own,it enhances the potency of certain pesticides such as carbamates,pyrethrins,pyrethroids,and rotenone. It is a semisynthetic derivative of safrole and is produced from the condensation of the sodium salt of 2-(2-butoxyethoxy) ethanol and the chloromethyl derivative of hydrogenated safrole (dihydrosafrole);or through 1,2-Methylenedioxybenzene.
Phthalates,or phthalate esters,are esters of phthalic acid. They are mainly used as plasticizers,i.e.,substances added to plastics to increase their flexibility,transparency,durability,and longevity. They are used primarily to soften polyvinyl chloride (PVC). Note that while phthalates are usually plasticizers,not all plasticizers are phthalates. The two terms are specific and unique and cannot be used interchangeably.
Endocrine disruptors,sometimes also referred to as hormonally active agents,endocrine disrupting chemicals,or endocrine disrupting compounds are chemicals that can interfere with endocrine systems. These disruptions can cause numerous adverse human health outcomes,including alterations in sperm quality and fertility;abnormalities in sex organs‚endometriosis‚early puberty‚altered nervous system or immune function;certain cancers;respiratory problems;metabolic issues;diabetes,obesity,or cardiovascular problems;growth,neurological and learning disabilities,and more. Found in many household and industrial products,endocrine disruptors "interfere with the synthesis,secretion,transport,binding,action,or elimination of natural hormones in the body that are responsible for development,behavior,fertility,and maintenance of homeostasis ."
Parabens are chemicals that are commonly used as preservatives in cosmetic and pharmaceutical products. Chemically,they are a series of parahydroxybenzoates or esters of parahydroxybenzoic acid. Research is being conducted to evaluate the potential health implications of paraben usage.
Bisphenol A (BPA) is a chemical compound primarily used in the manufacturing of various plastics. It is a colourless solid which is soluble in most common organic solvents,but has very poor solubility in water. BPA is produced on an industrial scale by the condensation reaction of phenol and acetone. Global production in 2022 was estimated to be in the region of 10 million tonnes.
Environmental toxicants and fetal development is the impact of different toxic substances from the environment on the development of the fetus. This article deals with potential adverse effects of environmental toxicants on the prenatal development of both the embryo or fetus,as well as pregnancy complications. The human embryo or fetus is relatively susceptible to impact from adverse conditions within the mother's environment. Substandard fetal conditions often cause various degrees of developmental delays,both physical and mental,for the growing baby. Although some variables do occur as a result of genetic conditions pertaining to the father,a great many are directly brought about from environmental toxins that the mother is exposed to.
Xenoestrogens are a type of xenohormone that imitates estrogen. They can be either synthetic or natural chemical compounds. Synthetic xenoestrogens include some widely used industrial compounds,such as PCBs,BPA,and phthalates,which have estrogenic effects on a living organism even though they differ chemically from the estrogenic substances produced internally by the endocrine system of any organism. Natural xenoestrogens include phytoestrogens which are plant-derived xenoestrogens. Because the primary route of exposure to these compounds is by consumption of phytoestrogenic plants,they are sometimes called "dietary estrogens". Mycoestrogens,estrogenic substances from fungi,are another type of xenoestrogen that are also considered mycotoxins.
Tetrabromobisphenol A (TBBPA) is a brominated flame retardant. The compound is a white solid,although commercial samples appear yellow. It is one of the most common flame retardants.
Triclocarban is an antibacterial chemical once common in,but now phased out of,personal care products like soaps and lotions. It was originally developed for the medical field. Although the mode of action is unknown,TCC can be effective in fighting infections by targeting the growth of bacteria such as Staphylococcus aureus. Additional research seeks to understand its potential for causing antibacterial resistance and its effects on organismal and environmental health.
Obesogens are certain chemical compounds that are hypothesised to disrupt normal development and balance of lipid metabolism,which in some cases,can lead to obesity. Obesogens may be functionally defined as chemicals that inappropriately alter lipid homeostasis and fat storage,change metabolic setpoints,disrupt energy balance or modify the regulation of appetite and satiety to promote fat accumulation and obesity.
Ecotoxicity,the subject of study in the field of ecotoxicology,refers to the biological,chemical or physical stressors that affect ecosystems. Such stressors could occur in the natural environment at densities,concentrations,or levels high enough to disrupt natural biochemical and physiological behavior and interactions. This ultimately affects all living organisms that comprise an ecosystem.
Bisphenol S (BPS) is an organic compound with the formula (HOC6H4)2SO2. It has two phenol functional groups on either side of a sulfonyl group. It is commonly used in curing fast-drying epoxy resin adhesives. It is classified as a bisphenol,and a close molecular analog of bisphenol A (BPA). BPS differentiates from BPA by possessing a sulfone group (SO2) as the central linker of the molecule instead of a dimethylmethylene group (C 2),which is the case of bisphenol A.
Reproductive toxicity refers to the potential risk from a given chemical,physical or biologic agent to adversely affect both male and female fertility as well as offspring development. Reproductive toxicants may adversely affect sexual function,ovarian failure,fertility as well as causing developmental toxicity in the offspring. Lowered effective fertility related to reproductive toxicity relates to both male and female effects alike and is reflected in decreased sperm counts,semen quality and ovarian failure.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a polychlorinated dibenzo-p-dioxin (sometimes shortened,though inaccurately,to simply 'dioxin') with the chemical formula C12H4Cl4O2. Pure TCDD is a colorless solid with no distinguishable odor at room temperature. It is usually formed as an unwanted product in burning processes of organic materials or as a side product in organic synthesis.
Health effects of pesticides may be acute or delayed in those who are exposed. Acute effects can include pesticide poisoning,which may be a medical emergency. Strong evidence exists for other,long-term negative health outcomes from pesticide exposure including birth defects,fetal death,neurodevelopmental disorder,cancer,and neurologic illness including Parkinson's disease. Toxicity of pesticides depend on the type of chemical,route of exposure,dosage,and timing of exposure.
Xenohormones or environmental hormones are compounds produced outside of the human body which exhibit endocrine hormone-like properties. They may be either of natural origin,such as phytoestrogens,which are derived from plants,or of synthetic origin. These compounds can cause endocrine disruption by multiple mechanisms including acting directly on hormone receptors,affecting the levels of natural hormones in the body,and by altering the expression of hormone receptors. The most commonly occurring xenohormones are xenoestrogens,which mimic the effects of estrogen. Other xenohormones include xenoandrogens and xenoprogesterones. Xenohormones are used for a variety of purposes including contraceptive &hormonal therapies,and agriculture. However,exposure to certain xenohormones early in childhood development can lead to a host of developmental issues including infertility,thyroid complications,and early onset of puberty. Exposure to others later in life has been linked to increased risks of testicular,prostate,ovarian,and uterine cancers.
Toxicodynamics,termed pharmacodynamics in pharmacology,describes the dynamic interactions of a toxicant with a biological target and its biological effects. A biological target,also known as the site of action,can be binding proteins,ion channels,DNA,or a variety of other receptors. When a toxicant enters an organism,it can interact with these receptors and produce structural or functional alterations. The mechanism of action of the toxicant,as determined by a toxicant’s chemical properties,will determine what receptors are targeted and the overall toxic effect at the cellular level and organismal level.
Bisphenol F is an organic compound with the chemical formula (HOC
6H
4)
2CH
2. It is structurally related to bisphenol A (BPA),a popular precursor for forming plastics,as both belong to the category of molecules known as bisphenols,which feature two phenol groups connected via a linking group. In BPF,the two aromatic rings are linked by a methylene connecting group. In response to concern about the health effects of BPA,BPF is increasingly used as a substitute for BPA.
Bisphenol A controversy centers on concerns and debates about the biomedical significance of bisphenol A (BPA),which is a precursor to polymers that are used in some consumer products,including some food containers. The concerns began with the hypothesis that BPA is an endocrine disruptor,i.e. it mimics endocrine hormones and thus has the unintended and possibly far-reaching effects on people in physical contact with the chemical.
Bruce A. Fowler is an American toxicologist,academic,and author. He is a co-owner and private consultant for Toxicology and Risk Assessment Consulting Services,and an adjunct professor at the Rollins School of Public Health at Emory University.