Processing technologies for poly(lactic acid)

In 1991, a group of 21 scientists gathered at the Wingspread Conference Center to discuss evidence of developmental alterations observed in wildlife populations after chemical exposures. There, the term "endocrine disruptor" was agreed upon to describe a class of chemicals including those that act as agonists and antagonists of the estrogen receptors (ERs), androgen receptor, thyroid hormone receptor, and others. This definition has since evolved, and the field has grown to encompass hundreds of chemicals. Despite significant advances in the study of endocrine disruptors, several controversies have sprung up and continue, including the debate over the existence of nonmonotonic dose response curves, the mechanisms of low-dose effects, and the importance of considering critical periods of exposure in experimental design. One chemical found ubiquitously in our environment, bisphenol-A (BPA), has received a tremendous amount of attention from research scientists, government panels, and the popular press. In this review, we have covered the above-mentioned controversies plus six additional issues that have divided scientists in the field of BPA research, namely: 1) mechanisms of BPA action; 2) levels of human exposure; 3) routes of human exposure; 4) pharmacokinetic models of BPA metabolism; 5) effects of BPA on exposed animals; and 6) links between BPA and cancer. Understanding these topics is essential for educating the public and medical professionals about potential risks associated with developmental exposure to BPA and other endocrine disruptors, the design of rigorously researched programs using both epidemiological and animal studies, and ultimately the development of a sound public health policy.

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Bisphenol-A and the Great Divide: A Review of Controversies in the Field of Endocrine Disruption

1.1. History
Formaldehyde was described in the year 1855 by the Russian scientist Alexander Michailowitsch Butlerow. The technical synthesis by dehydration of methanol was achieved in 1867 by the German chemist August Wilhelm von Hofmann. The versatility that makes it suitable for use in various industrial applications was soon discovered, and the compound was one of the first to be indexed by Chemical Abstracts Service (CAS). In 1944, Walker published the first edition of his classic work Formaldehyde.(1) Between 1900 and 1930, formaldehyde-based resins became important adhesives for wood and wood composites. The first commercial particle board was produced during World War II in Bremen, Germany. Since 1950, particle board has become an attractive alternative to solid wood for the manufacturing of furniture. Particle board and other wood-based panels were subsequently also used for the construction of housing. Adverse health effects from exposure to formaldehyde in prefabricated houses, especially irritation of the eyes and upper airways, were first reported in the mid-1960s. Formaldehyde emissions from particle boards bonded with urea formaldehyde resin were soon identified as the cause of the complaints. As a consequence, a guideline value of 0.1 ppm was proposed in 1977 by the former German Federal Agency of Health to limit human exposure in dwellings. Criteria for the limitation and regulation of formaldehyde emissions from wood-based materials were established in 1981 in Germany and Denmark. The first regulations followed in the United States in 1985 or thereabouts. In Germany and the United States, large-scale test chambers were used for the evaluation of emissions. Although the chamber method is very reliable, it is also time-consuming and expensive. This meant there was a strong demand for simple laboratory test methods.(2)

Formaldehyde in the Indoor Environment

Over 6 billion pounds per year of the estrogenic monomer bisphenol A (BPA) are used to manufacture polycarbonate plastic products, in resins lining metal cans, in dental sealants, and in blends with other types of plastic products. The ester bond linking BPA molecules in polycarbonate and resins undergoes hydrolysis, resulting in the release of free BPA into food, beverages, and the environment, and numerous monitoring studies now show almost ubiquitous human exposure to biologically active levels of this chemical. BPA exerts estrogenic effects through the classical nuclear estrogen receptors, and BPA acts as a selective estrogen receptor modulator. However, BPA also initiates rapid responses via estrogen receptors presumably associated with the plasma membrane. Similar to estradiol, BPA causes changes in some cell functions at concentrations between 1 pM and 1 nM, and the mean and median range of unconjugated BPA measured by multiple techniques in human pregnant maternal, fetal, and adult blood and other tissues exceeds these levels. In contrast to these published findings, BPA manufacturers persist in describing BPA as a weak estrogen and insist there is little concern with human exposure levels. Our concern with human exposure to BPA derives from 1) identification of molecular mechanisms mediating effects in human and animal tissues at very low doses, 2) in vivo effects in experimental animals caused by low doses within the range of human exposure, and 3) widespread human exposure to levels of BPA that cause adverse effects in animals.

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Large Effects from Small Exposures. III. Endocrine Mechanisms Mediating Effects of Bisphenol A at Levels of Human Exposure

Human exposure to bisphenol A

The concentrations of formaldehyde, acetaldehyde, propionaldehyde, and n-butyraldehyde in water were quantitatively determined by head space-gas chromatography/mass spectrometry (HS-GC/MS). Aqueous aldehydes were treated with o-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine (PFBOA) in a sealed vial at 60°C for 60 min. Head space was then analyzed by GC/MS. In comparison with electron ionization (EI) mass spectra, negative chemical ionization (NCI) mass spectra of PFBOA derivatives gave more spectral peaks of structural origin and with simple, characteristic fragmentation patterns. HS-GC/MS is highly sensitive for aqueous aldehydes because it eliminates interference from the water sample. The concentrations of various aldehydes in tap water and commercial mineral water were determined by HS-GC/MS. The following concentration ranges were detected for the individual aldehydes; formaldehyde, not detected (N.D.)-59 µg/l; acetaldehyde, N.D.-260 µg/l; propionaldehyde, N.D.- 0.9 µg/l; and n-butyraldehyde, N.D-0.3 µg/l.

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Analysis of Aldehydes in Water by Head Space-GC/MS

Reactions of sunscreen agents, octyl dimethyl-p-aminobenzoate (ODPABA) and octyl-p-methoxycinnamate (OMC), with hypochlorite in aqueous solution were investigated under the conditions that simulate swimming pool disinfection sites. Chlorination byproducts were determined by GC-MS. At a concentration of 9 μM, ODPABA reacted rapidly with free chlorine in the buffered solution at pH 7.0, OMC reacted with hypochlorite reasonably slowly under the same condition. ODPABA and OMC produced chlorine-substituted compounds as intermediates, which were decomposed to cleavaged products of ester-bond during the aqueous chlorination process. The chlorination intermediates of OMC exhibited weak mutagenic on Salmonella typhimurium TA100 strain without the S9 mix. The extent of the reactions depended on the chlorine dose, solution pH, and compound structures.

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Aquatic Fate of Sunscreen Agents Octyl-4-methoxycinnamate and Octyl-4-dimethylaminobenzoate in Model Swimming Pools and the Mutagenic Assays of Their Chlorination Byproducts

We examined whether orally administered bisphenol A transfers from the maternal rat to the fetus. After oral dose of 10mg/kg bisphenol A, it immediately appeared in maternal blood, and transferred into the fetuses. The concentration of bisphenol A in both maternal blood plasma and fetuses peaked within 1h after administration. The values were approximately 34 ppb and 11ppb, respectively. At 3h, the concentration of bisphenol A in maternal blood plasma had decreased to approximately 10% of the peak value. The 3-h decrease in fetuses was only about 40% of the peak, and by 24h, the fetal concentration had increased again to the nearly 70% of the peak value. The results suggest that bisphenol A might easily pass through the placental barrier, unlike sex hormones such as estrogen.

Passage of Bisphenol A into the Fetus of the Pregnant Rat

Interaction of 2,4,4'-trichloro-2'-hydroxydiphenyl ether with microsomal cytochrome P450-dependent monooxygenases in rat liver.

Triclosan, which is used widely as an antibacterial agent, was ubiquitously found in the water samples collected from the Tone Canal, Chiba, Japan. The concentrations of triclosan ranged from 11 to 31 ng/L. Higher concentrations of triclosan were observed in water samples collected from downstream, as compared to in the water samples collected upstream. The daily monitoring of a selected point from where the domestic wastewater inflow occurs showed that the triclosan levels in the water samples ranged from 55 to 134 ng/L; the levels of the loading amounts peaked from 10:00 to 12:00.

Sukeo Onodera

Papers

Analysis of Aldehydes in Water by Head Space-GC/MS

Aquatic Fate of Sunscreen Agents Octyl-4-methoxycinnamate and Octyl-4-dimethylaminobenzoate in Model Swimming Pools and the Mutagenic Assays of Their Chlorination Byproducts

Passage of Bisphenol A into the Fetus of the Pregnant Rat

Interaction of 2,4,4'-trichloro-2'-hydroxydiphenyl ether with microsomal cytochrome P450-dependent monooxygenases in rat liver.

Monitoring of Triclosan in the Surface Water of the Tone Canal, Japan