BBP (Butyl benzyl phthalate)

Project ID

2207

Category

IRIS

Added on

Dec. 4, 2012, 10:32 a.m.

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Journal Article

Abstract  Exposure to endocrine disrupting chemicals such as bisphenol A (BPA) and phthalates is prevalent among children and adolescents, but little is known regarding important sources of exposure at these sensitive life stages. In this study, we measured urinary concentrations of BPA and nine phthalate metabolites in 108 Mexican children aged 8-13years. Associations of age, time of day, and questionnaire items on external environment, water use, and food container use with specific gravity-corrected urinary concentrations were assessed, as were questionnaire items concerning the use of 17 personal care products in the past 48-h. As a secondary aim, third trimester urinary concentrations were measured in 99 mothers of these children, and the relationship between specific gravity-corrected urinary concentrations at these two time points was explored. After adjusting for potential confounding by other personal care product use in the past 48-h, there were statistically significant (p<0.05) positive associations in boys for cologne/perfume use and monoethyl phthalate (MEP), mono(3-carboxypropyl) phthalate (MCPP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and in girls for colored cosmetics use and mono-n-butyl phthalate (MBP), mono(2-ethylhexyl) phthalate (MEHP), MEHHP, MEOHP, and mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), conditioner use and MEP, deodorant use and MEP, and other hair products use and MBP. There was a statistically significant positive trend for the number of personal care products used in the past 48-h and log-MEP in girls. However, there were no statistically significant associations between the analytes and the other questionnaire items and there were no strong correlations between the analytes measured during the third trimester and at 8-13years of age. We demonstrated that personal care product use is associated with exposure to multiple phthalates in children. Due to rapid development, children may be susceptible to impacts from exposure to endocrine disrupting chemicals; thus, reduced or delayed use of certain personal care products among children may be warranted.

DOI
Journal Article

Abstract  P-doped TiO2 (PTIO) thin-films with different P contents were prepared using a sol-gel method. The thin-film samples were characterized using various techniques. The photocatalytic activity was evaluated by decomposing butyl benzyl phthalate under visible-light irradiation. The results showed that the transformation of anatase to the rutile phase was inhibited and grain growth of TiO2 was prevented by P doping. The results confirm that the doped P atoms existed in two chemical forms, and those incorporated in the TiO2 lattice may play a positive role in photocatalysis. The high photocatalytic activities of the PTIO thin-films may be the result of extrinsic absorption through the creation of oxygen vacancies, rather than excitation of the intrinsic absorption band of bulk TiO2. The PTIO can be recycled with little depression of the photocatalytic activity. After six cycles, the photocatalytic activity of the PTIO film was still higher than 98%. (c) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

DOI
Journal Article

Abstract  The degradation of Benzyl butyl phthalate (BBP) at low concentration (μg•L-1 range) by the direct UV irradiation, H2O2 oxidation and UV/H2O2 advance oxidation process was investigated in this study. The experiment results showed that the decomposition efficiency of UV or H2O2 was worse than that of UV/H2O2. Under the condition of 24.26μw•cm-2 UV irradiation and 2.49 mM H2O2, the degradation efficiency of BBP at low concentration was over 90% after 30 min. In addition, the solution pH was found to have no significant effect on the photo-degradation of BBP. The degradation of low concentration BBP in the tail water of municipal sewage plant was 84.23% with UV/H2O2 at the UV irradiation (24.26μw•cm-2) and H2O2 (2.49 mM) without adjusting pH.

Journal Article

Abstract  Human exposure to chemicals commonly encountered in our environment, like phthalates, is routinely assessed through urinary measurement of their metabolites. A particular attention is given to the specific population groups, such as obese, for which the dietary intake of environmental chemicals is higher. To evaluate the exposure to phthalates, nine phthalate metabolites (PMs) were analyzed in urine collected from obese individuals and a control population. Obese individuals lost weight through either bariatric surgery or a conservative weight loss program with dietary and lifestyle counseling. Urine samples were also collected from the obese individuals after 3, 6 and 12months of weight loss. Individual daily intakes of the corresponding phthalate diesters were estimated based on the urinary PM concentrations. A high variability was recorded for the levels of each PM in both obese and control urine samples showing the exposure to high levels of PMs in specific subgroups. The most important PM metabolite as percentage contribution to the total PM levels was mono-ethyl phthalate followed by the metabolites of di-butyl phthalate and di 2-ethyl-hexyl phthalate (DEHP). No differences in the PM levels and profiles between obese entering the program and controls were observed. Although paralleled by a significant decrease of their weight, an increase in the urinary PM levels after 3 to 6months loss was seen. Constant figures for the estimated phthalates daily intake were observed over the studied period, suggesting that besides food consumption, other human exposure sources to phthalates (e.g. air, dust) might be also important. The weight loss treatment method followed by obese individuals influenced the correlations between PM levels, suggesting a change of the intake sources with time. Except for few gender differences recorded between the urinary DEHP metabolites correlations, no other differences were observed for the urinary PM levels as a function of age, body mass index or waist circumference. Linear regression analysis showed almost no significance of the relationship between measured urinary PMs and serum free thyroxine, thyroid-stimulating hormone (TSH) for all obese individuals participating to the study, while for the control samples, several PMs were significantly associated with the serum TSH levels.

Journal Article

Abstract  In this work, phthalic acid esters (PAEs): dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate, and di-n-octyl phthalate in indoor dust (used as passive sampler) were investigated. The settled dust samples were collected from thirteen indoor environments from Palermo city. A fast and simple method using Soxhlet and GC-MS analysis has been optimized to identify and quantify the phthalates. Total phthalates concentrations in indoor dusts ranged from 269 to 4,831 mg/kg d.w. (d.w. = dry weight). The data show a linear correlation between total PAEs concentration and a single compound content, with the exclusion of the two most volatile components (DMP and DEP) that are present in appreciable amounts only in two samples. These results suggest that most of the PAEs identified in the samples of settled dust originate from the same type of material. This evidence indicates that, in a specific indoor environment, generally is not present only one compound but a mixture having over time comparable percentages of PAEs. Consequently, for routine analyses of a specific indoor environment, only a smaller number of compounds could be determined to value the contamination of that environment. We also note differences in phthalate concentrations between buildings from different construction periods; the total concentration of PAEs was higher in ancient homes compared to those constructed later. This is due to a trend to reduce or remove certain hazardous compounds from building materials and consumer goods. A linear correlation between total PAEs concentration and age of the building was observed (R = 0.71).

Journal Article

Abstract  Three waste water treatment plants (WWTPs) in Beijing were selected as cases to study the occurrence and fate of phthalates. Contents of di-methyl phthalate (DMP), di-ethyl phthalate (DEP), di-butyl phthalate (DBP), butyl-benzyl phthalate (BBP), di-octyl phthalate (DOP) and di-(2-ehtylhexyl) phthalate (DEHP) in influent, effluent of secondary setting tank and excess sludge in those WWTPs were determined. The mean concentration of DMP, DEP, DBP and DEHP are 0.98, 0.21 x 10(2), 0.27 x 10(2) and 0.15 x 10(2) microg x L(-1) respectively. BBP and DOP were not found in those WWTPs. Only DBP and DEHP were detected in dewatered sludge with mean concentration of 0.37 microg x kg(-1) and 0.31 x 10(3) microg x kg(-1) DW. The removal efficiency of DMP, DEP, DBP and DEHP varied from 68.3% -82.6%, 94.5% - 98.2%, 74.7% -95.0% and 90.5% -90.7% respectively. The main removal mechanism should be biodegradation and volatilization to the air. Higher concentration of DBP and DEHP in effluent and dewatered sludge should be concerned.

Technical Report

Abstract  Research published on the toxicological and environmental effects of phthalic-acid esters since 1978 was reviewed. Human studies were discussed. These have focused on the release and breakdown of di(2-ethylhexyl)phthalate (117817) (DEHP) and mono(ethylhexyl)phthalate (4376209) (MEHP) from polyvinyl-chloride materials used for blood storage or hemodialysis. The studies have shown that DEHP can be enzymatically converted into MEHP in stored plasma. The concentrations of DEHP and MEHP in stored blood samples are sufficient to cause toxicity in human cell lines. Autopsies have revealed that hemodialysis and transfusion patients may have increased tissue concentrations of phthalate esters. The significance of this finding is unknown since the frequency of detectable tissue phthalate concentrations in the general population is not known. Except for one Italian study using a small cohort, epidemiological studies on phthalate plasticizer workers have not found an increase in neurological symptoms or chromosome aberrations. The Italian study found a high prevalence of motor and sensorimotor polyneuropathy; however, the significance of the findings is limited because of the small number of cases. Studies in laboratory animals were discussed. These have shown that DEHP and other esters induce increases in liver weight and drug metabolizing enzymes in rats. DEHP also causes significant decreases in plasma testosterone in male rats. DEHP and MEHP have induced teratogenic effects; however, the doses used caused significant maternal toxicity. MEHP and DEHP have shown mutagenic activity in bacterial systems. Carcinogenesis bioassays using butylbenzyl-phthalate (85687) (BBP), diallyl-phthalate (131179), and DEHP conducted by the National Cancer Institute are in progress. Studies on mammalian metabolism of DEHP and butylglycolbutyl-phthalate (85701) were considered. Studies in fish and wildlife were discussed. BBP at concentrations of 0.5 to 5.0 milligrams per liter has been found to be toxic to algae, invertebrates, and fish. BBP seems to have a greater potential for bioconcentration than DEHP. Studies on the environmental fate and monitoring of phthalic-acid esters were discussed. These have shown that although there are many microorganisms in soil and water that can degrade phthalate esters, they do not apparently biodegrade rapidly.

Technical Report

Abstract  BIOSIS COPYRIGHT: BIOL ABS. RRM AMES SALMONELLA TEST PHOTOBACTERIUM-PHOSPHOREUM CARCINOGENS

Journal Article

Abstract  PURPOSE OF REVIEW: Phthalates are multifunctional chemicals used in personal care products, medications, and plastics. We reviewed the epidemiological literature examining the relationship between early life phthalate exposure and pediatric health outcomes.

RECENT FINDINGS: Five studies from Asia, Europe, and the United States suggest that childhood exposure to di-2-ethylhexyl phthalate (DEHP) and butylbenzyl phthalate (BBzP) may increase the risk of allergic diseases including asthma and eczema. Six studies from four different prospective cohorts report that gestational BBzP, DEHP, di-butyl phthalate (DBP), and di-ethyl phthalate (DEP) exposures are associated with alterations in infant/toddler physical development as well as parent-reported externalizing, internalizing, and autistic-like child behavior. However, there are inconsistencies related to the specific phthalates and behavioral domains. Two small studies report shorter anogenital distance among male infants with higher gestational phthalate exposure.

SUMMARY: Several epidemiological studies suggest fetal and childhood exposure to some phthalates may perturb normal development, with several studies consistently reporting increased risk of allergic diseases with DEHP and BBzP exposure. Although anticipatory guidance is not evidence-based at this time, providers can counsel concerned patients to reduce phthalate exposures in order to protect the developing fetus and child from potential adverse health outcomes.

Journal Article

Abstract  In this study we report the human plasma concentrations of some common endocrine disrupting chemicals (EDCs) in the Hong Kong population. We have analyzed 153 plasma samples for the contaminants by methods involving labeled standards spiked into the samples. Quantification was performed using high performance liquid chromatography tandem mass spectrometry for bisphenol-A (BPA) and perfluorinated compounds (PFCs), and gas chromatography mass spectrometry methods for phthalates. We found BPA, several types of PFCs and phthalates in over 90% of the plasma samples. Perfluorooctane sulfonate (PFOS) was the dominant PFC, followed by perfluroroctanoic acid (PFOA) and perfluorohexane sulfonate (PFHxS). Eight out of ten phthalates were detected, with bis(2-ethylhexyl) phthalate (DEHP) as the most abundant, followed by bis(2-methoxyethyl) phthalate (DMEP) and dioctyl phthalate (DnOP). The levels of PFOS, PFOA, PFHxS and perfluorohexanoic acid (PFHxA) were significantly higher in the male plasma samples (p<0.05), while the mean plasma levels of DEHP and n-butyl benzyl phthalate (BBP) were significantly higher in the young age group (p<0.02). The presence of the selected EDCs in human blood plasma indicates common exposure routes among different population cohorts. Although the plasma levels of the EDCs were comparable to other countries, regular monitoring of human blood EDC contamination levels is necessary to provide a time-trend database for the estimation of exposure risk and to formulate appropriate public health policy.

Journal Article

Abstract  Phthalate diesters, widely used in flexible plastics and consumer products, have become prevalent contaminants in the environment. Human exposure is ubiquitous and higher phthalate metabolite concentrations documented in patients using medications with phthalate-containing slow release capsules raises concerns for potential health effects. Furthermore, animal studies suggest that phthalate exposure can modulate circulating hormone concentrations and thus may be able to adversely affect reproductive physiology and the development of estrogen sensitive target tissues. Therefore, we conducted a systematic review of the epidemiological and experimental animal literature examining the relationship between phthalate exposure and adverse female reproductive health outcomes. The epidemiological literature is sparse for most outcomes studied and plagued by small sample size, methodological weaknesses, and thus fails to support a conclusion of an adverse effect of phthalate exposure. Despite a paucity of experimental animal studies for several phthalates, we conclude that there is sufficient evidence to suggest that phthalates are reproductive toxicants. However, we note that the concentrations needed to induce adverse health effects are high compared to the concentrations measured in contemporary human biomonitoring studies. We propose that the current patchwork of studies, potential for additive effects and evidence of adverse effects of phthalate exposure in subsequent generations and at lower concentrations than in the parental generation support the need for further study.

Journal Article

Abstract  We conducted an epidemiologic study to test the hypothesis that women who smoke have reduced fertility. Data on smoking history and number of noncontracepting cycles until conception were collected from 678 pregnant women. Thirty-eight percent of nonsmokers conceived in their first cycle compared with 28% of smokers. Smokers were 3.4 times more likely to have taken greater than a year to conceive compared with nonsmokers. After adjusting for potential confounding variables by Cox proportional hazards regression, fertility of smokers was estimated to be 72% of the fertility of nonsmokers. Heavy smokers experienced lower fertility than did light smokers (57% and 75% of the pregnancy rate of nonsmokers, respectively). Fertility was not affected by the husband's smoking. These data provide evidence that reduced fertility should be added to the growing list of reproductive hazards of cigarette smoking.

Journal Article

Abstract  Natural hormones and some synthetic chemicals spread into our surrounding environment share the capacity to interact with hormone action and metabolism. Exposure to such compounds can cause a variety of developmental and reproductive detrimental abnormalities in wildlife species and, potentially, in human. Many experimental and epidemiological data have reported that exposure of the developing fetus or neonate to environmentally relevant concentrations of some among these endocrine disrupters induces morphological, biochemical and/or physiological disorders in brain and reproductive organs, by interfering with the hormone actions. The impact of such exposures on the hypothalamic-pituitary-gonadal axis and subsequent sexual maturation is the subject of the present review. We will highlight epidemiological human studies and the effects of early exposure during gestational, perinatal or postnatal life in female rodents.

DOI
Journal Article

Abstract  During recent decades the prevalence of IgE-mediated (atopic) allergic diseases in Western Europe and the USA has been increasing dramatically. It has been suggested that one possible cause is the presence in the environment of chemicals that may act as adjuvants, enhancing immune and allergic responses. Certain commonly used phthalate plasticizers such as butyl benzyl phthalate (BBP) have been implicated in this way. In the current experiments, the impact of BBP, applied by a physiologically relevant exposure route, on the vigour of immune responses induced in BALB/c strain mice has been examined. Mice were immunized via subcutaneous injection with the reference allergen ovalbumin (OVA) and received concurrent topical treatment with doses of BBP that induced significant changes in liver weight. The generation of specific anti-OVA IgE and IgG1 antibodies was measured by passive cutaneous anaphylaxis and by enzyme-linked immunosorbant assays, respectively. Topical administration of BBP was without impact on anti-OVA IgE antibody responses, regardless of whether BBP was applied locally or distant to the site of OVA immunization. However, same-site treatment with high-dose BBP (100 mg) did result in a modest elevation in anti-OVA IgG1 antibody production, a subclass of antibody used as a surrogate marker of IgE responses. Taken together with human exposure data, these results suggest that the doses of phthalate encountered in the home environment are unlikely to be a major factor contributing to the increased incidence of asthma and allergy in the developed world.

Journal Article

Abstract  We developed and evaluated a total toxic units modeling approach for predicting mean toxicity as measured in laboratory tests for Great Lakes sediments containing complex mixtures of environmental contaminants (e.g., polychlorinated biphenyls, polycyclic aromatic hydrocarbons, pesticides, chlorinated dioxins, and metals). The approach incorporates equilibrium partitioning and organic carbon control of bioavailability for organic contaminants and acid volatile sulfide (AVS) control for metals, and includes toxic equivalency for planar organic chemicals. A toxic unit is defined as the ratio of the estimated pore-water concentration of a contaminant to the chronic toxicity of that contaminant, as estimated by U.S. Environmental Protection Agency Ambient Water Quality Criteria (AWQC). The toxic unit models we developed assume complete additivity of contaminant effects, are completely mechanistic in form, and were evaluated without any a posteriori modification of either the models or the data from which the models were developed and against which they were tested. A linear relationship between total toxic units, which included toxicity attributable to both iron and un-ionized ammonia, accounted for about 88% of observed variability in mean toxicity; a quadratic relationship accounted for almost 94%. Exclusion of either bioavailability components (i.e., equilibrium partitioning control of organic contaminants and AVS control of metals) or iron from the model substantially decreased its ability to predict mean toxicity. A model based solely on un-ionized ammonia accounted for about 47% of the variability in mean toxicity. We found the toxic unit approach to be a viable method for assessing and ranking the relative potential toxicity of contaminated sediments.

DOI
Journal Article

Abstract  Phthalate esters (PAEs) are ubiquitous in the indoor environment, owing to their use in consumer products. People spend a considerable amount of time indoors. As a result, human exposure to indoor contaminants is of great concern. People are exposed to phthalates through inhalation and dermal absorption of indoor air. In this study, the concentrations, characteristics and carcinogenic risks of gasphase and particle-phase phthalates in indoor air from bedroom, living room and study room of 10 newly decorated apartments in Hangzhou, China were first investigated. The mean concentration of phthalates (gas-phase and particle-phase) present in household air was 12 096.4 ng m(-3), of which diethyl phthalate (DEP), butylbenzyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP) were the most abundant compounds with concentrations of 2290 ng m(-3), 3975 ng m(-3) and 2437 ng m(-3), respectively, totally accounting for 72.0% of Sigma(6)PAEs. Contamination levels of phthalates varied in different compartments. The concentration of phthalates was the highest 17363.7 ng m(-3) in living room, followed with 11 389.5 ng m(-3) in study room, and the lowest 9739.1 ng m(-3) in bedroom. It was also found that phthalates mainly accumulated in gaseous form in household air. DEHP posed the greatest health risk to children aged 1-2. Carcinogenic risk of DEHP was evaluated to be 3.912 x 10(-5), and was 39 times higher than the limit set by the U.S. EPA.

DOI
Journal Article

Abstract  To investigate the levels and possible determinants of phthalate esters (PEs) in settled house dust from urban dwellings with young children, dust was collected from 215 urban houses in Nanjing, China, and 145 outdoor settled dust samples were collected nearby. Six PEs were measured by gas chromatography/mass spectrometry. All PEs were detected in the dust from approximately 90% of the houses, with the exception of dioctyl phthalate (DOP), which had only a 59% detection rate. Di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP) were the most abundant PEs, with geometric means of 110 and 16.4 mu g g(-1), respectively, and maximal concentrations 9950 and 2150 mu g g(-1). Factor analysis showed that DBP, DEHP and benzyl butyl phthalate (BBP) might come from the same source and were significantly influenced by the use of solid-wood floor wax. High BBP, DEHP, DOP and total PE levels were associated with indices of dampness, and high DOP was associated with humidifier use. In conclusion, six PEs are ubiquitous in urban settled house dust in Nanjing, China, and both plastic materials and cosmetic and personal care products are important sources. Flooring material, dampness and humidifier use potentially influence house dust PE levels.

Journal Article

Abstract  BACKGROUND: There is concern over potential neurobehavioral effects of prenatal phthalate exposures, but available data are inconsistent.

OBJECTIVES: To examine associations between prenatal urinary concentrations of phthalate metabolites and neurobehavioral scores among children.

METHODS: We measured phthalate metabolite concentrations in urine samples from 153 pregnant participants in the Study for Future Families, a multicenter cohort study. Mothers completed the Child Behavior Checklist when the children were 6-10 years of age. We estimated overall and sex-specific associations between phthalate concentrations and behavior using adjusted multiple regression interaction models.

RESULTS: In boys concentrations of mono-isobutyl phthalate were associated with higher scores for inattention (β = 0.27; 95% CI: 0.04, 0.50), rule-breaking behavior (β = 0.20; 95% CI: 0.01, 0.38), aggression (β = 0.34; 95% CI: 0.09, 0.59), and conduct problems (β = 0.39; 95% CI: 0.20, 0.58), while the molar sum of di-(2-ethylhexyl) phthalate metabolites was associated with higher scores for somatic problems (β = 0.15; 95% CI: 0.03, 0.28). Higher monobenzyl phthalate concentrations were associated with higher scores for oppositional behavior (β = 0.16; 95% CI: 0.01, 0.32) and conduct problems (β = 0.21; 95% CI: 0.06, 0.37) in boys, but with reduced anxiety scores in girls (β = -0.20; 95% CI: -0.39, -0.01). In general, the associations reported above were close to the null among girls. Model coefficients represent the difference in the square-root transformed outcome score associated with a 1-unit increase in log-transformed metabolites.

CONCLUSIONS: Our results suggest associations between exposure to certain phthalates in late pregnancy and behavioral problems in boys. Given the few studies on this topic and methodological and population differences among studies, additional research is warranted.

Journal Article

Abstract  A GC/MS method was developed for the identification and quantification of 14 phthalates: 8 phthalates classified H360 (DBP, DEHP, BBP, DMEP, DnPP, DiPP, DPP and DiBP), 3 phthalates proposed to be forbidden in medical devices (DnOP, DiNP and DiDP) and 3 other phthalates none regulated (DMP, DCHP and DEP) which may interfere with hormone function. In order to identify and quantify other plasticizers that are commonly used in PVC medical devices such as DEHP substitute, 5 non-phthalate plasticizers (ATBC, DEHA, DEHT, TOTM, and DINCH) were included in this study. Analyses are carried out on a GC/MS system with electron impact ionization mode (EI). The separation of plasticizers is obtained on a cross-linked 5%-phenyl/95%-dimethylpolysiloxane capillary column 30m×0.25mm (i.d.)×0.25μm film thickness using a gradient temperature. Compounds quantification is performed by external calibration using an internal standard. Validation elements on standard solutions were determined using the ISO 12787 standard approach. Plasticizers are extracted from PVC medical devices using THF for dissolving the PVC part of the sample followed by precipitation of the PVC by addition of ethanol. The supernatant is injected into a GC/MS system after dilution in ethanol. Different validation elements, including extraction recoveries for all compounds or for DEHP a cross-validation of the extraction process using the European pharmacopoeia monograph 3.1.14 as reference method, are discussed. Results obtained on 61 medical devices in PVC and 12 raw materials used as plasticizers are given.

Technical Report

Abstract  BIOSIS COPYRIGHT: BIOL ABS. RRM POLYCYCLIC AROMATIC HYDROCARBONS SUBSTITUTED PHENOLS PHTHALATE ESTERS

Journal Article

Abstract  in their 10th or 11th years, while others who are equally healthy may not experience menarche until they 'are 14, 15, or even older. Menarche is, however, only a single event in the combination of physical changes which constitute puberty. The adolescent growth spurt, the development of the breasts, and the growth of the pubic hair occur more or less concurrently, and take, on the average, about 3 years from beginning to completion, with menarche occurring usually in the latter half of this period (Tanner, 1962). At present we lack detailed information about the rate at which girls progress through the stages of puberty and about the relation of one event to another. Only longitudinal studies (i.e. studies in which the same individuals are examined repeatedly over a period of time) can provide this information, which would be helpful both to the clinician in distinguishing the normal from the abnormal, and to the neuro-endocrinologist in constructing hypotheses about the mechanisms by which puberty is controlled. Present knowledge is based on studies carried out on small numbers of children in the United States a generation ago, together with some German studies of a similar period (for literature see Tanner, 1962).

Technical Report

Abstract  The Fourth National Report on Human Exposure to Environmental Chemicals, Updated Tables, September 2013 provides nationally representative biomonitoring data that has become available since the publication of the Fourth National Report on Human Exposure to Environmental Chemicals, 2009. The Updated Tables, September 2013 includes all the updates previously provided in Updated Tables, July 2010 through Updated Tables, March 2013. The Updated Tables, September 2013 present data for 91 chemicals measured in serum pooled samples that have not been reported in any previous Updated Tables. Since publication of the Fourth Report, 2009, 201 chemicals have updated tables and 49 chemicals have been added, for a total of 250 chemicals presented in these Updated Tables.

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