Levels of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in breast milk in Shanghai, China: A temporal upward trend

Human milk samples were collected from 150 mothers in 2011 and 2012 in Shanghai, China and analyzed for 17 polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and 12 dioxin-like polychlorinated biphenyls (DL-PCBs). The up-bound Toxic Equivalent Quantity (TEQ) ranged from 0.27 to 16.8 pg TEQ/g lipid (mean 5.4 pg TEQ/g lipid) for ∑PCDD/Fs and from 0.75 to 10.2 pg TEQ/g lipid (mean 2.9 pg TEQ/g lipid) for ∑DL-PCBs. TEQs in our study were lower than those in most countries worldwide, and displayed a notable uptrend, in contrast with those in China's national survey in 2007. TEQs in mother milks from urban areas were higher than those from rural areas, and an orderly distribution was found in four geographical regions: Eastern China>Central China≈Southwestern China>Northwestern China. Levels of analytes in Shanghai native mothers' milk ranked the first among those from all provinces and cities investigated. Migrant mothers to Shanghai from other inland provinces could potentially represent the population for exposure and risk assessment in their birth and grown-up places. Both the distribution and the uptrend were associated with release of these pollutants due to rapid industrialization and urbanization in China. Fine correlations were observed between TEQs and age of mothers, and weak correlations between TEQs and consumption of meat & meat products. Participants, who preferred both fresh water and marine fish to freshwater fish only, were prone to be exposed to higher level of PCBs. The estimated daily intake (EDI) doses for breastfed neonates entirely exceeded the tolerable intake dose by WHO.

Co-exposure to polycyclic aromatic hydrocarbons, benzene and toluene and their dose-effects on oxidative stress damage in kindergarten-aged children in Guangzhou, China

Polycyclic aromatic hydrocarbons (PAHs), benzene and toluene (BT) are ubiquitous toxic pollutants in the environment. Children are sensitive and susceptible to exposure to these contaminants. To investigate the potential oxidative DNA damage from the co-exposure of PAHs and BT in children, 87 children (aged 3-6) from a kindergarten in Guangzhou, China, were recruited. Ten urinary PAHs and four BT metabolites, as well as 8-hydroxy-2'-deoxyguanosine (8-OHdG, a biomarker of oxidative DNA damage)in urine, were determined using a liquid chromatography tandem mass spectrometer. The results demonstrated that the levels of PAHs and BT in children from Guangzhou were 2-30 times higher than those in children from the other countries based on a comparison with recent data from the literature. In particular, the difference is more substantial for pyrene and volatile BT. Co-exposure to PAHs and BT could lead to additive oxidative DNA damage. Significant dose-effects were observed between the sum concentration of urinary monohydroxylated metabolites of PAHs (∑OH-PAHs), the sum concentration of the metabolites of BT (∑BT) and 8-OHdG levels. Every one percent increase in urinary PAHs and BT generated 0.33% and 0.02% increases in urinary 8-OHdG, respectively. We also determined that the urinary levels of PAHs and BT were negatively associated with the age of the children. Moreover, significant differences in the levels of ∑OH-PAHs and ∑BT were determined between 3- and 6-year-old children (p<0.05), which may be caused by different metabolism capabilities or inhalation frequencies. In conclusion, exposure to PAHs or BT could lead to oxidative DNA damage, and 8-OHdG is a good biomarker for indicating the presence of DNA damage. There exists a significant dose-effect relationship between PAH exposure, BT exposure and the concentration of 8-OHdG in urine. Toddlers (3-4 years old) face a higher burden of PAH and BT exposure compared with older children.

Determination of organochlorines, polychlorinated biphenyls and polybrominated diphenyl ethers in human hair: estimation of external and internal exposure

A novel method was developed for the analysis of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in human hair samples. External contaminants of hair were extracted with acetone under sonication, while washed hair was further hydrolyzed in formic acid and acetone (1:4, v/v) with microwave assisted extraction (MAE) for internal contaminant measurements. Both internal and external extracts were cleaned up with gel permeation chromatography (GPC) and then solid phase extraction (SPE), before analyzed by a large volume injection-gas chromatography-tandem mass spectrometry (LVI-GC-MS/MS) using triple quadruple mass analyzer. Good linearity (R(2)⩾ 0.996) was established within a concentration range between 0.1 and 100 ng mL(-)(1) among all target analytes. The method was validated for accuracy, precision and sensitivity. The developed method is intended to be cost effective and robust for the routine human hair analysis of PCBs, PBDEs and OCPs including acid-labile OCPs. The described method has been applied in pilot biomonitoring study and the preliminary data suggested that the contaminant profiles with the use of partial least-squares analysis discriminant analysis (PLA-DA) could be useful in differentiating external and internal exposure.

Pooling samples for "top-down" molecular exposomics research: the methodology

BACKGROUND

Exposomics is the cutting-edge concept of screening the environmental risk factors for disease. In the novel "top-down" approach, we estimate the molecular exposome by measuring all body fluid analytes in a case-controlled study. However, to detect diverse pollutants, a sufficient sample size and multiple analytical methods are required. This may lead to dramatically increased costs and research workload.

METHODS

To help reduce complexity, we suggest a sample pooling strategy along with a scheme for combining both general unknown or multi-targeted screening with targeted analysis. The sample pooling method was tested using computer simulations.

RESULTS

By comprehensively analysis of pooled samples, it is possible to identify environmental risk factors. Factors are initially screened in the pooled case and control population samples, then in the randomized grouped and pooled case and control subpopulation samples. In the sample grouping, five or more pools were suggested for groups having 30 individuals per pool.

CONCLUSIONS

This study suggests that sample pooling is a useful strategy for exposomics research, which provides a hypothesis-free method for pollutant risk screening.

Matrix effects in analysis of dialkyl phosphate metabolites of organophosphate pesticides in urine by gas chromatography/tandem mass spectrometer

Urinary dialkyl phosphate metabolites (DAPs) are used as biomarkers to evaluate human exposure to organophosphate pesticides. The objective was to evaluate potential artifacts in urinary DAPs analysis during sample preparation and method calibration. Diluted urine pools were commonly used to prepare calibration standards to minimize the effects due to the complexity of urine matrix. Matrix effects on measurements of DAPs were evaluated by spiking known amount of standards into distilled water, synthetic urine and diluted urine pool. Different matrices resulted in similar concentrations detected for all target compounds, except dimethylphosphate (DMP) with the deviation of measurement as large as eight times the spiked amount. In this study, we also found that urinary particles, which usually appeared after thawing frozen human urine samples, could affect the measurements of DAPs, especially DMP and diethylthiophosphate (DETP). Results of DAPs measurements in three types of sample matrices, i.e. urine without particles, urine with particles and particles only were compared. DETP could be subject to large error during this preparation step. The use of deuterated and (13)C(12)-labeled DAPs as internal standards is also evaluated. Overall, these issues can cause misidentification and inaccuracies, which may significantly affect the data quality.

DETECTION OF LACTOBACILLI IN MONTHLY MAIL-IN STOOL SAMPLES FROM 3-18 MONTHS OLD INFANTS AT GENETIC RISK FOR TYPE 1 DIABETES

The feasibility to detect lactobacilli in mail-in infant stools collected monthly from 3-18 months old children was investigated. The aim was to determine total lactobacilli and Lactobacillus plantarum (L. plantarum) content (ng/g feces) in 50 infants each from Colorado (648 samples), Finland (624 samples) and Sweden (685 samples) who participated in the TEDDY (The Environmental Determinants of Diabetes in the Young) study. Total lactobacilli content varied markedly between 5 and 16,800 ng/g feces in the three clinical sites within and between individuals especially in infants. L.plantarum also varied markedly intra- and inter-individually from <0.5 - 736 ng/g feces. A higher variability of total lactobacilli was found before 10 months of age than after in the three different clinical sites. Sweden had the lowest total lactobacilli content compared to Colorado and Finland while the L.plantarum content was higher in Sweden. Mail-in stool samples from infants should prove useful in analyzing probiotics in childhood.

Environmental exposure to arsenic may reduce human semen quality: associations derived from a Chinese cross-sectional study

BACKGROUND

Recent observations in in vitro and in vivo models suggest that arsenic (As) is an endocrine disruptor at environmentally-relevant levels. When exposed to As, male rats and mice show steroidogenic dysfunction that can lead to infertility. However, the possible effects of As on human male semen quality remain obscure.

METHODS

We monitored the profile of As species in the urine of a reproductive-age human cohort and assessed its association with semen quality. Men (n = 96) were recruited in an infertility clinic from July 2009 to August 2010 in the Affiliated Hospital of Chongqing Institute for Population and Family Planning. Five urinary As species were analyzed by high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Clinical information on the semen volume, sperm concentration and motility was employed to catalogue and evaluate semen quality according to WHO guidelines. As species concentrations in addition to other continuous variables were dichotomized by the medians and modelled as categorical variables in order to explore using the binary logistic regression possible associations between As exposure and semen quality.

RESULTS

Urinary concentrations (geometric mean ± SD, μg g(-1) creatinine) of different As species were 7.49 (± 24.8) for AsB, 20.9 (± 13.7) for DMA, 2.77 (± 3.33) for MMA, and 4.03 (± 3.67) for Asi (Asi(III )and Asi(V)). DMA concentrations above the median were significantly associated with below-reference sperm concentrations (P = 0.02) after adjusting for age, body mass index (BMI), abstinence, smoking and drinking habits. In addition, smoking was positively associated with MMA.

CONCLUSION

Reduced parameters in human semen quality are positively associated with As exposure in a reproductive-age Chinese cohort.

Preliminary study of children's exposure to PAHs and its association with 8-hydroxy-2'-deoxyguanosine in Guangzhou, China

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous air pollutants generated mainly from incomplete combustion such as automobile exhaust and cigarette smoke. Oxidative stress is believed to be involved in carcinogenesis, and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) was used as the biomarker to assess such DNA damage. The children's urinary PAH metabolite (OH-PAHs) level were explored in Guangzhou and their associations with 8-OHdG. Two groups of subjects were selected: (1) one group (n=39, 6-7 years old) from an elementary school situated near a heavy traffic road (polluted area) and (2) another group (n=35, 4-6 years old) from a kindergarten situated in a corner of the main campus of a big university (non-polluted area). Urinary 8-OHdG and nine urinary monohydroxylated PAH metabolites were measured, including 2-hydroxynaphthalene (2-OHN), 2-hydroxyfluorene (2-OHF), 2-, 3-, 4-, 9-hydroxyphenanthrene (2-, 3-, 4-, 9-OHPhe), 1-hydroxypyrene (1-OHP), 6-hydroxychrysene (6-OHChr) and 3-hydroxybenzo(a)pyrene (3-OHBaP). All other PAH metabolites were detected in urine samples from both children groups except for 6-OHChr and 3-OHBaP. Levels of 2-OHN, 2-OHF, 3-OHPhe, 9-OHPhe and 1-OHP were significantly different between two groups (P<0.05, T-test). The elementary school children from the polluted area had higher urinary levels of 2-OHN, 2-OHF, 2-, 3-, 4-OHPhe and 1-OHP ((9.10±7.39, 3.72±2.91, 0.32±0.50, 0.37±0.28, 0.23±0.29 and 0.64±0.07 μmol/mol creatinine, respectively) than those from the control group. The results suggested that heavy traffic pollution led to higher PAH body burden. There existed no significant difference for urinary 8-OHdG concentration between two groups (p>0.05, T-test), and no strong correlations between the individual OH-PAHs and 8-OHdG. However, the urinary 8-OHdG concentration in the elementary school children from the traffic polluted area was slightly higher than those in the non-polluted area (20.87±14.42 μmol/mol creatinine vs. 16.78±13.30 μmol/mol creatinine). It may be that the potential co-exposure of the children to other pollutants affects 8-OHdG concentration besides the PAHs.

High postnatal exposures to polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) via breast milk in California: does BDE-209 transfer to breast milk?

Breast milk samples collected during 2003-2005 from 82 first-time mothers in 24 communities located throughout California contained levels of polybrominated diphenyl ethers (∑(tri-hexa (8))PBDEs; median = 53.3 ng/g lw, range = 9.60-1291) and polychlorinated biphenyls (∑(12)PCBs; median = 73.4 ng/g lw, range = 22.2-433) that are among the highest in the world. PBDE levels varied 100-fold. BDE-47 was the dominant PBDE congener, with levels exceeding the U.S.EPA Reference Dose (RfD) for neurodevelopmental toxicity (100 ng/kg/day) in most (60%) breast milk samples. In some samples, BDE-209 (2/82) and/or BDE-153 (5/82) were the dominant congeners, suggesting that BDE-209 can transfer to breast milk and/or break down in the mother and transfer to the nursing infant as the lower-brominated PBDEs associated with adverse effects. PBDE levels in California breast milk are approaching those of PCBs, and the trend PBDEs > PCBs may continue as PBDEs migrate from products to the indoor and outdoor environments.

Stress failure plays a major role in the development of high-altitude pulmonary oedema in rats

Hypoxia and exertion are considered as the two main factors in the development of high-altitude pulmonary oedema (HAPE), however its pathophysiology remains unclear. Therefore, we established a model in which 32 Sprague-Dawley rats were randomly assigned to normoxic rest, hypoxic rest, normoxic exercise and hypoxic exercise. An altitude of 4,700 m was simulated using hypobaric hypoxia, while exercise consisted 48 h walk with 15-20 min breaks every 4 h. Arterial blood gas, bronchoalveolar lavage (BAL), lung wet-to-dry weight (W/D) ratio and histological measurements were conducted on each animal. In rats exercising in hypoxia, BAL protein and lung W/D ratio were significantly increased but no changes in BAL leukotriene B(4) and immunoglobulin M were observed. In the same group, lung histology showed typical haemorrhagic lung oedema and disruption of both alveolar epithelium and capillary endothelium while hypoxia or exertion alone only induced slight endothelium and epithelium swelling/disruption. Our study established a direct link between histological and physiological evidence of HAPE-like symptoms and we demonstrated that hypoxia and exertion can synergistically induce HAPE-like symptoms in Sprague-Dawley rats without inducing lung inflammation. We therefore propose that alveolar epithelium and capillary endothelium stress failure play a major role in the development of HAPE.

Improving auscultatory blood pressure measurement with electronic and computer technology: the visual auscultation method

BACKGROUND

The auscultatory method is used as the reference standard in all prevalent protocols for validation of noninvasive blood pressure measuring devices, and a validation study is essentially based on the comparison between the device and observer measurements. Thus, the objectivity and accuracy of observer measurements are crucial to the validation result.

METHODS

To provide observers with more objective information about an auscultatory measurement so that sufficient information to make measurements with greater potential objectivity and accuracy can be available, a computerized data acquisition and analysis system has been developed. It cannot only acquire and store Korotkoff sound, cuff pressure, and oscillometric pulse signals, as well as the sphygmomanometer image, but it also can display the waveforms of the three signals and the sphygmomanometer video while playing the synchronous Korotkoff sounds. With this system, observers can make their measurements via the visual auscultation method, that is to say, by watching those waveforms, instead of the sphygmomanometer, while listening for synchronized Korotkoff sounds. The system was validated according to the International Protocol (IP).

RESULTS

The result showed that all the differences between system measurements by the visual auscultation method and observer measurements by the conventional auscultatory method were within 4 mm Hg.

CONCLUSIONS

The visual auscultation method achieved a high degree of accuracy, and human observers can be replaced by the system in the validation study of blood pressure measuring devices.

Concentrations and time trends of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in aquatic bird eggs from San Francisco Bay, CA 2000-2003

Concentrations of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were measured in 169 avian eggs. We analyzed randomly collected eggs of two species of piscivorous birds: Caspian tern (Sterna caspia) (n=78) and Forster's tern (Sterna forsteri) (n=76). We also analyzed fail-to-hatch eggs from two species protected under the Federal Endangered Species Act of 1973, that breed in the San Francisco Bay region: the piscivorous California Least tern (Sterna antillarum brownii) (n=11) and the omnivorous California Clapper rail (Rallus longirostris obsoletus) (n=4). San Francisco Bay eggs were collected annually for four years (2000-2003), and additional 20 eggs were collected and analyzed from Gray's Harbor, Washington in 2001. Geometric mean PBDE concentrations did not significantly differ in the three tern species, but concentrations in eggs from the fail to hatch California Clapper rail eggs were significantly lower than those found in the randomly collected tern eggs. Median concentrations of SigmaPBDEs in Caspian tern eggs for 2000-2003 were 2410, 4730, 3720 and 2880 ng/g lipid weight (lw), respectively, in Forster's terns 1820, 4380, 5460 and 3600 ng/g lw, respectively, and in California Least terns for 2001 and 2002 were 5060 and 5170 ng/g lw, respectively. In contrast, median SigmaPBDEs concentration in California Clapper rail eggs for 2001 was 379 ng/g lw. Five PBDEs were the major congeners found and decreased in the order BDE-47, -99, -100, -153, and -154. BDE-32, -28, -71, -66, -85, -183 were less prevalent, minor congeners, as was BDE-209, which was measured in a subset of samples. PBDE concentrations in bird eggs from San Francisco Bay were site related. There was no significant difference in PBDE concentrations in Caspian tern eggs from San Francisco Bay and Gray's Harbor, WA. Average PBDE concentrations in eggs did not significantly increase over the period 2000-2003.

Depuration of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in breast milk from California first-time mothers (primiparae)

BACKGROUND

Little is known about the rates of loss (depuration) of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) from mothers during lactation. Depuration rates affect infant exposure to chemicals during breast-feeding, and fetal and lactational transfers during subsequent pregnancies.

OBJECTIVE

Our objective in this study was to estimate depuration rates of PBDEs and PCBs using serial samples of breast milk.

METHOD

Nine first-time mothers (primiparae) each collected samples at 4, 6, 8, 12, 16, 20, and 24 weeks after birth. Nine additional primiparae each collected two samples at varying time intervals (18 to > 85 weeks after birth). Analytical precision was assessed to evaluate the accuracy of measured monthly percentage declines in PBDEs and PCBs.

RESULTS

The four major PBDE congeners decreased 2 or 3% +/- 1% per month over the 6-month period. These decreases were consistent over a 50-fold range (21-1,330 ng/g lipid weight) of initial PBDE concentrations in breast milk. The change in PCB-153 ranged from + 0.3% to -0.6% per month, with heterogeneous slopes and greater intraindividual variability. PBDE and PCB concentrations declined 1% per month over longer periods (up to 136 weeks).

CONCLUSIONS

Our data indicate that PBDEs and PCBs are not substantially (4-18%) reduced in primiparae after 6 months of breast-feeding. Consequently, the fetal and lactational exposures for a second child may not be markedly lower than those for the first. Participants were volunteers from a larger study population (n = 82), and were typical in their PBDE/PCB levels and in many demographic and lifestyle factors. These similarities suggest that our results may have broader applicability.

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in breast milk from the Pacific Northwest

Breast milk samples from 40 first-time mothers from the Pacific Northwest of the US and Canada were analyzed for polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs). Total PBDEs (summation operator PBDEs), calculated by summing values for the 12 PBDEs congeners analyzed, ranged from 6 to 321 ppb (lipid weight) (mean=96 ppb; median=50 ppb). In approximately 40% of the women (15/40), summation operator PBDEs>100 ppb lw in their milk, and four samples had levels >250 ppb lw. PBDE 47 was the dominant congener in most samples, whereas PBDE 153 was predominant in a few (3/40). summation operator PCBs were calculated by summing values for the 82 PCB congeners analyzed, and ranged from 49 to 415 ppb (lipid weight) (mean=147 ppb; median=126 ppb). approximately 30% of the mothers (13/40) have summation operator PBDEs> summation operator PCBs in their milk samples, and approximately 65% (25/40) have BDE 47>PCB 153 in breast milk samples, with BDE 47 averaging 3-fold greater levels than PCB 153. Clearly, the lower brominated PBDEs are surpassing PCBs as a major environmental concern in North America, and are likely affecting significant portions of the populations in these regions. PBDEs have become a major persistent organic pollutant. However, there are no positive correlations between levels of summation operator PBDEs and summation operator PCBs, or between levels of PBDE 47 and PCB 153, suggesting there may be some differences in exposure pathways for PBDEs and PCBs in humans.

High body burdens of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in California women

Following our first report on elevated polybrominated diphenyl ether (PBDE) concentrations in California women, we expanded our investigation to include diverse groups of local women. We analyzed additional adipose and serum samples collected in the late 1990s from San Francisco Bay Area women participating in a breast cancer study and in a reproductive study, respectively. Adipose samples (n = 32) were analyzed by low-resolution mass spectrometry in negative-ion chemical ionization mode, whereas serum samples (n = 50) were analyzed by dual-column gas chromatography with electron capture detection. The results confirmed our earlier findings. Concentrations of 2,2,4,4 -tetrabromodiphenyl ether (BDE-47) in contemporary California women ranged between 5 and 510 ng/g lipid, with a median (16.5 ng/g lipid) 3-10 times higher than those reported from Europe. In contrast, PBDEs were not measurable in any of 420 archived serum samples collected in the 1960s from San Francisco Bay Area women participating in a study of child development. BDE-47 concentrations did not increase with age or with concentrations of a polychlorinated biphenyl (PCB-153), suggesting other routes of exposure in addition to diet. Rising body burdens of endocrine-disrupting chemicals such as PBDEs may pose a potential public health threat.

Lessons from the polybrominated diphenyl ethers (PBDEs): precautionary principle, primary prevention, and the value of community-based body-burden monitoring using breast milk

Levels of chemicals in humans (body burdens) are useful indicators of environmental quality and of community health. Chemical body burdens are easily monitored using breast milk samples collected from first-time mothers (primiparae) with infants 2-8 weeks of age. Currently, there is no body-burden monitoring program using breast milk in the United States, although ad hoc systems operate successfully in several European countries. In this article we describe the value of such monitoring and important considerations of how it might be accomplished, drawing from our experiences with pilot monitoring projects. Breast milk has several advantages as a sampling matrix: It is simple and noninvasive, with samples collected by the mother. It monitors body burdens in reproductive-age women and it estimates in utero and nursing-infant exposures, all important to community health. Time-trend data from breast milk monitoring serve as a warning system that identifies chemicals whose body burdens and human exposures are increasing. Time trends also serve as a report card on how well past regulatory actions have reduced environmental chemical exposures. Body-burden monitoring using breast milk should include educational programs that encourage breast-feeding. Finally, and most important, clean breast milk matters to people and leads to primary prevention--the limiting of chemical exposures. We illustrate these advantages with polybrominated diphenyl ethers (PBDEs), a formerly obscure group of brominated flame retardants that rose to prominence and were regulated in Sweden when residue levels were found to be rapidly increasing in breast milk. A community-based body-burden monitoring program using breast milk could be set up in the United States in collaboration with the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). WIC has a large number of lactating first-time mothers: It has 6,000 clinics nationwide and serves almost half (47%) the infants born in the United States. Educational programs (e.g., those run by WIC) are needed that encourage breast-feeding, especially in lower-income communities where breast-feeding rates are low and where breast-feeding may help protect the infant from the effects of environmental chemical exposures. Education is also needed about reducing chemical body burdens. A body-burden monitoring program would provide valuable data on time trends, background levels, and community hot spots in need of mitigation and follow-up health studies; develop analytic methods for new chemicals of concern; and archive breast milk samples for future analyses of other agents.

Early chronic aluminium exposure impairs long-term potentiation and depression to the rat dentate gyrus in vivo

As an important neurotoxin, aluminium can cause cognitive dysfunctions and mental diseases. Previous studies have reported that aluminium impaired long-term potentiation (LTP) in vivo and in vitro. Here, we utilise two models of synaptic plasticity, LTP and long-term depression (LTD) to study the effects of aluminium on synaptic plasticity in vivo. Neonatal Wistar rats were chronically exposed to aluminium from birth to weaning via the milk of dams fed with 0.3% aluminium chloride solution. Excitatory postsynaptic potential (EPSP) and population spikes (PS) were recorded from the dentate gyrus (DG) of adult rats by electrically stimulating the perforant path. THE FOLLOWING RESULTS WERE OBTAINED: (1) The input/output function indicated that, as compared to controls, aluminium increased the baseline amplitude of the PS, but decreased the baseline slope of EPSP. (2) Aluminium significantly prevented LTD in PS (controls: 77.36+/-6.7%, n=7; aluminium-exposed: 102.01+/-9.1%, n=7; P<0.05) and decreased the LTD amplitude in EPSP (controls: 76.61+/-4.1%, n=7; aluminium-exposed: 94.31+/-7.9% n=7, P<0.05). (3) Aluminium reduced the amplitude of LTP in both PS (controls: 190+/-16.1%, n=7; aluminium-exposed: 135+/-9.7%, n=7; P<0.05) and EPSP (control: 132+/-9.3%, n=7; aluminium-exposed: 115+/-10.6%, n=7; P<0.05). As for LTD and LTP, PS was impaired more seriously than EPSP in aluminium-exposed rats. (4) Aluminium exposure decreased the paired-pulse facilitation (PPF) of PS at 30-150 ms interpulse interval (IPI), and reduced 93.5% of PPF at 80 ms IPI in PS (controls: 243.4+/-39.8%, n=7; aluminium-exposed: 149.9+/-12.3%, n=7). There was no significant difference in EPSP of PPF. From these results we conclude that aluminium exposure in neonatal rats thus reduces the amplitude of LTP and PPF and blocks the induction of LTD in the DG. We suggest that aluminium affects both presynaptic and postsynaptic mechanisms of synaptic transmission.