Sources of human exposure: overview of water supplies as sources of boron

Boron (B) is widely distributed in surface and groundwaters predominantly as undissociated boric acid, and is found in ocean waters at a mean level of approx 4.6 mg B/L. A recent analysis of US surface waters indicated that the 10th, 50th, and 90th percentile B levels were 0.010, 0.076, and 0.387 mg B/L, respectively. The same study found that the 50th and 90th percentile B levels in California drinking waters were 0.10 and 0.40 mg B/L, respectively. The overall mean B concentration in Canadian surface waters in 1988 was reported to be 0.16 mg B/L, with a few stations reporting concentrations above 2.0 mg B/L. Unusually high levels of B have been measured in human water supplies of northern Chile, with concentrations ranging from 0.31 to 15.2 mg B/L. River water sources of B in the UK and Northern Italy were found to range from 0.002 to 0.87 mg B/L, respectively, whereas German drinking waters had median and maximum B levels of 0.02 and 0.18 mg B/L, respectively. Bottled mineral water also represents a source of B exposure based on the largest reported survey of US and European products, with a mean level of 0.75 mg B/L and a range from <0.005 to 4.35 mg B/L. Thus, B intake from drinking water is highly variable and dependent on the geographic source, the quantities of water consumed and the water sources used to bottle other beverages.     

Can sunbleak Leucaspius delineatus or topmouth gudgeon Pseudorasbora parva disperse through saline waters?

In order to determine the potential for the invasive fishes sunbleak Leucaspius delineatus and topmouth gudgeon Pseudorasbora parva to disperse through saline waters their behaviour and physiology were investigated during exposure to salinities of 10·0 and 12·5. Increased salinity caused an increase in whole body cortisol in both species, but sunbleak and topmouth gudgeon showed very different metabolic and behavioural responses to the salinity stress. Sunbleak displayed increased swimming activity in brackish water, which may be important for dispersal through saline waters in the wild, although there were increased metabolic costs associated with this behaviour. Conversely, topmouth gudgeon showed a reduction in both swimming activity and metabolic rate in brackish waters. A pronounced depression in food intake (70–80%) was shown by both species during the salinity exposures. Both sunbleak and topmouth gudgeon, however, showed a full recovery of food intake within 24 h following return to fresh water. Despite the fact that exposure to saline waters is stressful, and affects both physiology and behaviour, rapid recovery of appetite after return to fresh water suggests that short-term use of brackish waters is a feasible dispersal route for sunbleak and topmouth gudgeon in the wild.     

Modeling Human Exposure to Phthalate Esters: A Comparison of Indirect and Biomonitoring Estimation Methods

Humans are potentially exposed to phthalate esters (PEs) through ingestion, inhalation, and dermal contact. Studies quantifying exposure to PEs include “biomarker studies” and “indirect studies.” Biomarker studies use measurements of PE metabolites in urine to back-calculate exposure to the parent diester, while indirect studies use the concentration of the PE in each medium of exposure and the rate of intake of that medium to quantify intake of the PE. In this review, exposure estimates from biomarker and indirect studies are compiled and compared for seven PEs to determine if there are regional differences and if there is a preferred approach. The indirect and biomarker methods generally agree with each other within an order of magnitude and discrepancies are explained by difficulties in accounting for use of consumer products, uncertainty concerning absorption, regional differences, and temporal changes. No single method is preferred for estimating intake of all PEs; it is suggested that biomarker estimates be used for low molecular weight PEs for which it is difficult to quantify all sources of exposure and either indirect or biomarker methods be used for higher molecular weight PEs. The indirect methods are useful in identifying sources of exposure while the biomarker methods quantify exposure.     

The isotopic composition of anthropogenic boron and its potential impact on the environment

The present study investigates the isotopic composition of anthropogenic boron (B) and its potential affects on the environment. The isotopic ratios of B in synthetic products from the main ores in the world have been measured by negative thermal ionization mass spectrometry. The data show that the isotopic compositions of Na-borate products and washing powders overlap with those of natural Na-borate minerals. In contrast, the¹¹B/¹⁰B ratios of synthetic Ca-borate and Na/Ca borate products are significantly lower (by 15 permil) and overlap with those of the natural Ca-borate minerals. Consequently, the original isotopic signature of natural borate minerals is not modified during the manufacturing process of synthetic products. The B isotopic composition of domestic wastewater from Israel and Riverside, California suggests that B in sewage is derived from Na-borate components used in detergents. Since B, like other inorganic ions, is not removed during conventional sewage treatment, it accumulates in domestic wastewater. Although the B concentration in pristine groundwaters is generally low (<0.05 mg/L), contaminant sources (e.g., wastewater) are relatively enriched in B (0.5–1 mg/L). The isotopically distinguished signature of borate compounds is used to trace groundwater contamination.     

Theoretical study of the intake of trace elements (nutrients and contaminants) via total diet in some geographical areas of Spain

The aim of this study was to monitor exposure to heavy metal contaminants from habitual diets and to estimate the health risk for the consumer by comparing the analyzed content with the acceptable daily intake (ADI). This study is based on the household consumption as assessed by the National Institute of Statistics (INE) and our department. The number of food groups (237) consumed by the population (national and the 17 Autonomy Communities) is considered. A list of the metal content of foods is included. The data were collected from reports issued by the Ministry of Health, other official organizations, and from specialized literature. The results show that the intakes of arsenic (0.019 mg/person/d), mercury (0.004 mg/person/d), and lead (0.082 mg/person/d) do not reach the ADI, but that of cadmium exceeds the ADI in some geographical areas. The intake of zinc and chromium does not exceed the dietetic recommendations.     

Effects of manufactured nanomaterials on fishes: a target organ and body systems physiology approach

Manufactured nanomaterials (NM) are already used in consumer products and exposure modelling predicts releases of ng to low μg l(-1) levels of NMs into surface waters. The exposure of aquatic ecosystems, and therefore fishes, to manufactured NMs is inevitable. This review uses a physiological approach to describe the known effects of NMs on the body systems of fishes and to identify the internal target organs, as well as outline aspects of colloid chemistry relevant to fish biology. The acute toxicity data, suggest that the lethal concentration for many NMs is in the mg l(-1) range, and a number of sublethal effects have been reported at concentrations from c. 100 μg to 1 mg l(-1). Exposure to NMs in the water column can cause respiratory toxicity involving altered ventilation, mucus secretion and gill pathology. This may not lead, however, to overt haematological disturbances in the short term. The internal target organs include the liver, spleen and haematopoietic system, kidney, gut and brain; with toxic effects involving oxidative stress, ionoregulatory disturbances and organ pathologies. Some pathology appears to be novel for NMs, such as vascular injury in the brain of rainbow trout Oncorhynchus mykiss with carbon nanotubes. A lack of analytical methods, however, has prevented the reporting of NM concentrations in fish tissues, and the precise uptake mechanisms across the gill or gut are yet to be elucidated. The few dietary exposure studies conducted show no effects on growth or food intake at 10-100 mg kg(-1) inclusions of NMs in the diet of O. mykiss, but there are biochemical disturbances. Early life stages are sensitive to NMs with reports of lethal toxicity and developmental defects. There are many data gaps, however, including how water quality alters physiological responses, effects on immunity and chronic exposure data at environmentally relevant concentrations. Overall, the data so far suggest that the manufactured NMs are not as toxic as some traditional chemicals (e.g. some dissolved metals) and the innovative, responsible, development of nanotechnology should continue, with potential benefits for aquaculture, fisheries and fish health diagnostics.     

能量标签技术及其在红树林生态系统能流研究中的应用

传统上认为红树林输出的有机质产生巨大的能流,支持了巨大的河口和近岸水域生态系统的次级生产。但能量标签技术的研究结果却显示红树林输出的有机质的作用并没有如此巨大。用红树碎屑难消化特性来解释此现象,此外数学模型模拟分析发现潮汐的稀释作用也可以解释这种现象。但这两者都不能解释,在其他初级生产者稀少时,红树材输出的有机质可以被大量利用的现象。在有红树林的河口和近海岸水域生态系统中,藻类等非红树初级生产者具有比红树植物更高的初级生产力,而且更容易被动物获得和消化。可以认为是藻类等巨大初级生产力的竞争作用导致红树初级生产在消费者组织中很难被发现,如此上面提到的难题就能得到很好的解决。此外能量标签技术检测出的是红树的初级生产在消费者组织中的相对比率,不是绝对数量值,从此角度看,能量标签技术的结果与传统观点不是矛盾而是互相补充的关系。由此推测红树的初级生产应该还是被消费者所利用,只是它们在消费者初级营养来源组成中占的比例并不大,但其绝对数量并不少。这与传统观点认为的红树的初级生产被大量利用,支撑了具有巨大的次级生产稍有不同。此外,能量标签技术在红树林生态系统中的适用性尚未检验;计算食物组成的数学工具不是很完善;实验设计上考虑的不够全面;对定量研究有一定的影响。     

Migration of phthalates from plastic products to model solutions

The aim of this investigation was to determine the level and rate of migration of phthalates, compounds used as plastic softeners, from various plastic products into model solutions and to assess the possible adverse effects of the phthalate amounts released on human health, thus to contribute to harmonization of the opinions on the maximal allowed human exposure to these compounds through environmental factors. Nine specimens of plastic toys, 16 specimens of plastic food containers and 10 specimens of other plastic consumer goods were analyzed. The specimens of plastic products were submitted to 10-day action of model solutions. Three model solutions were used: distilled water, 10% ethyl alcohol, and 3% acetic acid. Identification and quantification of the phthalates released were performed by the method of gas chromatography on days 1, 5 and 10 of exposure, at a detection limit of 0.005 microgram/kg. On day 10, the highest level of released phthalates (54.5 mg/kg) was measured in distilled water, followed by 44.4 mg/kg in 3% acetic acid and 32.3 mg/kg in 10% ethyl alcohol. According to plastic product categories, the highest pooled level of phthalates released to all three solutions was recorded for plastic toys (66.2 mg/kg), followed by food containers (37.6 mg/kg) and other consumer goods (27.4 mg/kg). According to plastic product categories, toys showed the most rapid phthalate release, with 65.4% (43.3 of 66.2 mg/kg) of the pooled level of phthalates released to all three solutions recorded on day 1. As indicated by the study results, the levels of phthalates released would not present a hazard for human health, not even over a prolonged period of time. However, data on the highest and fastest pooled phthalate release from plastic toys, and this especially to distilled water simulating salivary action, point to the need of continuous evaluation and amendments of the legislation on phthalates in consumer goods.     

Estimation of Dietary Intake of Inorganic Arsenic in U.S. Children

Arsenic is a natural component of the environment and is ubiquitous in soils, water, and the diet. Because dietary intake can be a significant source of background exposure to inorganic arsenic (the most toxicologically significant form), accurate intake estimates are needed to provide a context for risk management of arsenic exposure. Intake of inorganic arsenic by adults is fairly well characterized, but previous estimates of childhood intake were based on inorganic arsenic analyses in a limited number of foods (13 food types). This article estimates dietary intake for U.S. children (1 to 6 years of age) based on reported inorganic arsenic concentrations in 38 foods and in water used in cooking those foods (inorganic arsenic concentration of 0.8 μg/L), and U.S. Department of Agriculture food consumption data. This information is combined using a probabilistic software model to extract food consumption patterns and compute exposure distributions. The mean childhood dietary intake estimate for inorganic arsenic was 3.2 μg/day with a range of 1.6 to 6.2 μg/day for the 10th and 95th percentiles, respectively. For both the mean and 95th percentile inorganic arsenic intake rates, intake was predominantly contributed by grain and grain products, fruits and fruit juices, rice and rice products, and milk.     

Linking the Use of Scented Consumer Products to Consumer Exposure to Polycyclic Musk Fragrances

Synthetic organic chemicals are ingredients of many consumer products used daily. Consumers are therefore constantly exposed to a broad spectrum of synthetic organic chemicals, which might be irritants or have other effects harmful to human health, in the consumption phase of the product life cycle. Relevant examples are the polycyclic musk fragrances that make up an important group of synthetic fragrance compounds. Using a scenario-based approach, we simulate various product uses and calculate the resulting dermal exposure to the musk fragrances 6-acetyl-1,1,2,4,4,7-hexamethyltetraline and hexahydro-hexamethyl-cyclopenta (γ)-2-benzopyran for a wide spectrum of consumer products. The product spectrum was selected from scented personal care products and household cleansing agents. Exposure to musk fragrances is calculated with two dermal exposure models, and results are presented for female and male European consumers. The variability of required inputs is accounted for by assuming minimal, average or median, and maximal values for important model parameters. The study identifies a limited number of types of scented consumer products as significantly contributing to daily dermal consumer exposure to musk fragrances. Exposure levels resulting from the simultaneous use of these products and the number of exposed consumers are investigated.     

Susceptibility of male reproductive system to bisphenol A,an endocrine disruptor: Updates from epidemiological and experimental evidence

Bisphenol A (BPA) is an omnipresent environmental pollutant. Despite being restrictions in-force for its utilization, it is widely being used in the production of polycarbonate plastics and epoxy resins. Direct, low-dose, and long-term exposure to BPA is expected when they are used in the packaging of food products and are used as containers for food consumption. Occupationally, workers are typically exposed to BPA at higher levels and for longer periods during the manufacturing process. BPA is a known endocrine disruptor chemical (EDC), that causes male infertility, which has a negative impact on human life from emotional, physical, and societal standpoints. To minimize the use of BPA in numerous consumer products, efforts and regulations are being made. Despite legislative limits in numerous nations, BPA is still found in consumer products. This paper examines BPA's overall male reproductive toxicity, including its impact on the hypothalamic-pituitary-testicular (HPT) axis, hormonal homeostasis, testicular steroidogenesis, sperm parameters, reproductive organs, and antioxidant defense system. Furthermore, this paper highlighted the role of non-monotonic dose–response (NMDR) in BPA exposure, which will help to improve the overall understanding of the harmful effects of BPA on the male reproductive system.     

Dependence of Intake Fraction on Release Location in a Multimedia Framework

A defining feature of industrial ecology is the design of processes to minimize any disruption of the functioning of the natural ecosystem that supports life, including human beings. The extent of human exposure to anthropogenic contaminants in the environment is a complex function of the amount of chemical emitted, its physicochemical properties and reactivity, the nature of the environment, and the characteristics of the pathways for human exposure, such as inhalation, dermal contacts, and intake of food and water. For some chemicals, the location of emissions relative to areas of high population density or intense food production may also be an important factor. We explore the relative importance of these variables using the regionally segmented Berkeleyf-Trent (BETR) North America contaminant fate model and data for food production patterns and population density for North America. The model is applied to fourfff contaminants emitted to air: benzene, carbon tetrachloride, benzo-a-pyrene, and 2,3,7,8 tetrachlorodibenzo-pff-dioxin. The total continental intake fraction (iF), relating exposure quantity to emission quantity, is employed as a metric for assessing population exposure to these contaminants. Results show that the use of continentally averaged parameters for population density and food production provides an accurate estimate of the median of iF calculated for emissions in individual regions; however, iF can range from this median by up to 3 orders of magnitude, especially for chemicals transferred to humans through foods. The locations of population and food production relative to sources of chemicals are important variables that should be considered when assessing the possible human health impacts of chemical emissions as in life-cycle assessment.     

在培养基和食料中添加铅和镉对轮虫种群动态的影响

由于工业活动的影响,墨西哥水体环境中的重金属浓度在上升.浮游动物,尤其是轮虫类,由于对环境变化十分敏感而且是淡水中的常见组成部分,因此被广泛用于生态毒理试验以确定水质标准.在不同的胁迫途径下(如通过培养基或食料),重金属的毒性是不同的.在本研究中,通过在轮虫Brachionus rubens的培养基和食料中添加重金属这两种途径,我们评估了镉和铅的效应.对于这两种重金属,均采用将轮虫置于含0.5×106个/ml绿藻的培养基中或每天喂食经5倍于LC50值的金属处理(1,2和4h)的绿藻.对于在培养基中添加镉,使用了三个毒性水平(0.1,0.2和0.4 mg/L),铅的浓度分别为0.005,0.010 和0.015 mg/L.基于LC50的数据,B.rubens对铅的敏感性要比镉高24倍.镉浓度为0.4 mg/L时,培养基中加入镉造成B.rubens的生长趋缓.而喂食经不同时间处理的绿藻后,轮虫的密度随着食料在重金属中处理时间的延长而减小.培养基中或食料中添加铅时,轮虫种群生长的的趋势与在镉处理下的情况类似.随着培养基中重金属浓度的增加,每天种群增长率(r值)会减小.在培养基和食料处理两种不同途径下,r值会在0.33(对照)到0.02 d-1(经重金属处理)间变化[动物学报 51(1)46-52,2005].     

The effects of buprenorphine, nalbuphine and butorphanol alone or following halothane anaesthesia on food and water consumption and locomotor movement in rats.

Locomotor activity and food and water consumption are potentially indices of post-operative pain in laboratory rodents, but it is important to establish whether these variables are directly affected by opioid analgesics or by halothane anaesthesia in normal rats. The effects of three opioids, buprenorphine, nalbuphine and butorphanol administered alone or following halothane anaesthesia, were studied in groups of normal non-operated adult Wistar rats. All 3 analgesics affected food intake and activity levels, but had little or no effect on water intake. Buprenorphine caused a significant elevation of activity levels and a reduction in food intake at clinical doses (0.01 and 0.05 mg/kg s/c). Nalbuphine (0.5, 1 and 2 mg/kg s/c) caused a reduction in food intake but had a smaller stimulatory effect on locomotion. Butorphanol (0.4 mg/kg s/c) caused a reduction in food intake and elevation in activity. These results suggest that water consumption is likely to be a more reliable variable to use when assessing post-operative pain and the efficacy of analgesics in rats.     

Estimation of Multimedia Inorganic Arsenic Intake in the U.S. Population

Arsenic is widely distributed in the environment by natural and human means. The potential for adverse health effects from inorganic arsenic depends on the level and route of exposure. To estimate potential health risks of inorganic arsenic, the apportionment of exposure among sources of inorganic arsenic is critical. In this study, daily inorganic arsenic intake of U.S. adults from food, water, and soil ingestion and from airborne particle inhalation was estimated. To account for variations in exposure across the U.S., a Monte Carlo approach was taken using simulations for 100,000 individuals representing the age, gender, and county of residence of the U.S. population based on census data. Our analysis found that food is the greatest source of inorganic arsenic intake and that drinking water is the next highest contributor. Inhalation of airborne arsenic-containing particles and ingestion of arsenic-containing soils were negligible contributors. The exposure is best represented by the ranges of inorganic arsenic intake (at the 10^th and 90^th percentiles), which were 1.8 to 11.4 µg/day for males and 1.3 to 9.4 µg/day for females. Regional differences in inorganic arsenic exposure were due mostly to consumption of drinking water containing differing inorganic arsenic content rather than to food preferences.     

Escalating Worldwide use of Urea – A Global Change Contributing to Coastal Eutrophication

While the global increase in the use of nitrogen-based fertilizers has been well recognized, another change in fertilizer usage has simultaneously occurred: a shift toward urea-based products. Worldwide use of urea has increased more than 100-fold in the past 4 decades and now constitutes >50% of global nitrogenous fertilizer usage. Global urea usage extends beyond agricultural applications; urea is also used extensively in animal feeds and in manufacturing processes. This change has occurred to satisfy the world’s need for food and more efficient agriculture. Long thought to be retained in soils, new data are suggestive of significant overland transport of urea to sensitive coastal waters. Urea concentrations in coastal and estuarine waters can be substantially elevated and can represent a large fraction of the total dissolved organic nitrogen pool. Urea is used as a nitrogen substrate by many coastal phytoplankton and is increasingly found to be important in the nitrogenous nutrition of some harmful algal bloom (HAB) species. The global increase from 1970 to 2000 in documented incidences of paralytic shellfish poisoning, caused by several HAB species, is similar to the global increase in urea use over the same 3 decades. The trend toward global urea use is expected to continue, with the potential for increasing pollution of sensitive coastal waters around the world.     

Npvf: Hypothalamic Biomarker of Ambient Temperature Independent of Nutritional Status

The mechanism by which mice, exposed to the cold, mobilize endogenous or exogenous fuel sources for heat production is unknown. To address this issue we carried out experiments using 3 models of obesity in mice: C57BL/6J+/+ (wild-type B6) mice with variable susceptibility to obesity in response to being fed a high-fat diet (HFD), B6. Ucp1-/- mice with variable diet-induced obesity (DIO) and a deficiency in brown fat thermogenesis and B6. Lep-/- with defects in thermogenesis, fat mobilization and hyperphagia. Mice were exposed to the cold and monitored for changes in food intake and body composition to determine their energy balance phenotype. Upon cold exposure wild-type B6 and Ucp1-/- mice with diet-induced obesity burned endogenous fat in direct proportion to their fat reserves and changes in food intake were inversely related to fat mass, whereas leptin-deficient and lean wild-type B6 mice fed a chow diet depended on increased food intake to fuel thermogenesis. Analysis of gene expression in the hypothalamus to uncover a central regulatory mechanism revealed suppression of the Npvf gene in a manner that depends on the reduced ambient temperature and degree of exposure to the cold, but not on adiposity, leptin levels, food intake or functional brown fat.     

Dietary molar ratios of phytate: Zinc and millimolar ratios of phytate × calcium: Zinc in South Koreans

The zinc nutritional status in south Koreans was established by evaluation of zinc, calcium and phytate intakes, the molar ratio of phytate: zinc, and the millimolar ratio of phytate × calcium: zinc. The intakes of iron and magnesium were also estimated. Sampling was designed so that it was representative of the national population. Two-day food records were used for the calculation of nutrient intakes, using food consumption data from the 1995 National Nutrition Survey (’95NNS) for South Korea. Daily intakes of zinc and calcium were estimated to be 10.1 mg/d and 426.5 mg/d, respectively, and those of iron and magnesium were 15.2 mg/d and 268.0 mg/d, respectively. The estimated daily phytate intake was 1676.6 mg/d. The ratio of phytate: zinc was 15.9 mol/d and that of phytate × calcium: zinc was 168.9 mmol/d. The ratio in millimoles per 4.2 MJ (1000 kcal) of phytate × calcium: zinc was 91.8. The major food groups for zinc intake were meat, poultry and their products (43%), and cereals and grain products (18%). Sixty-two percent of zinc was from animal food sources. Cereal and grain products supplied most of the phytate intake (46%) followed by seasonings, fruits, and legumes and their products. The major food source of phytate was rice (39%). The results of the study raise concern about the suboptimal zinc status in relation to the Western diet.     

Methyl Ethyl Ketone Safety Characterization for Infants and Children: Assessment in the USEPA Voluntary Children's Chemical Evaluation Program

A safety characterization specific to children was performed for methyl ethyl ketone (MEK) according to the guidelines of the Voluntary Children's Chemical Evaluation Program (VCCEP). The characterization indicates that MEK exposures are not expected to pose an acute or chronic risk to children. Hazard information, summarized as per the VCCEP Tier structure, indicated no need for additional studies. All exposure pathways potentially relevant to children were considered, including child contact with environmental media, food, drinking water, parental transfer to child (human milk or dermal contact), direct consumer product use, and presence during product use. The assessment found that exposures from anthropogenic sources that children may encounter on a daily basis are very low, and in particular well below the chronic inhalation and oral health benchmarks (RfC and RfD) derived by the U.S. Environmental Protection Agency (USEPA). Indoor uses of consumer products can result in higher acute exposures, but these are short-lived and also fall below chronic benchmarks adjusted to an acute timeframe. In addition, MEK is rapidly metabolized and excreted, thus acute exposures do not lead to an increase in body burden over time. The USEPA concluded the VCCEP submission sufficiently characterized potential risks to children, and that no additional toxicity tests were needed for MEK.     

The site of action of naloxone in suppressing food and water intake in rats

Previous studies have shown that naloxone causes a decrease in food and water intake; however, the site of this action has not been determined. We investigated this problem by giving bilateral injections of 15 μg/rat of naloxone into the lateral ventricles of cannulated, food and water deprived rats. This treatment caused a significant decrease in food intake when compared to saline injected controls. Water intake in naloxone-treated animals did not differ significantly from that of saline-treated controls during the one hour test period. The total dose of naloxone given centrally, 15 μg, did not produce a change in eating or drinking if given peripherally. The findings imply that naloxone exerts its effect on food intake at a central site. A dose-related and significant suppression of water intake was seen after treatment with nalaxone peripherally (1, 3, and 10 mg/kg, i.p.) in rats with either subdiaphragmatic vagotomy (vag) or a sham vagotomy (sham). Although a significant suppression of food intake was seen in the sham rats, no supression of food intake was seeen in the vag rats at any dose of naloxone tested. In rats pretreated with methyl atropine (5 mg/kg, i.p.), naloxone (3 mg/kg, i.p.) was equivalent to saline in that it did not decrease food intake. However, nalaxone did cause a significant decrease in water intake in methylatropine pre-treated rats. These results suggest that the suppression of food intake by naloxone has a central site of action which is mediated by the vagus, and specifically by vagal efferents, since the effect was blocked by methylatropine. The results also suggest that naloxone's effect on water intake is mediated by a different mechanism than that involved with food intake.