Validation of a terrestrial food chain model.

An increasingly important topic in risk assessment is the estimation of human exposure to environmental pollutants through pathways other than inhalation. The Environmental Protection Agency (EPA) has recently developed a computerized methodology (EPA, 1990) to estimate indirect exposure to toxic pollutants from Municipal Waste Combuster emissions. This methodology estimates health risks from exposure to toxic pollutants from the terrestrial food chain (TFC), soil ingestion, drinking water ingestion, fish ingestion, and dermal absorption via soil and water. Of these, one of the most difficult to estimate is exposure through the food chain. This paper estimates the accuracy of the EPA methodology for estimating food chain contamination. To our knowledge, no data exist on measured concentrations of pollutants in food grown around Municipal Waste Incinerators, and few field-scale studies have been performed on the uptake of pollutants in the food chain. Therefore, to evaluate the EPA methodology, we compare actual measurements of background contaminant levels in food with estimates made using EPA's computerized methodology. Background levels of contaminants in air, water, and soil were used as input to the EPA food chain model to predict background levels of contaminants in food. These predicted values were then compared with the measured background contaminant levels. Comparisons were performed for dioxin, pentachlorophenol, polychlorinated biphenyls, benzene, benzo(a)pyrene, mercury, and lead.     

Assessment of health risks upon exposure to methylated mercury

Accumulation of a toxic agent (2-4-fold maximum allowable concentrations) was found in the fish caught in the polluted area of the water storage basin of the Angara river. The authors quantified a risk for major pathological syndromes in individuals exposed to mercury on fish ingestion and assayed biosubstrates for the substance. The integral risk of major pathological syndromes in the potentially mercury loaded persons increased by 62.1% with age and only by 17.1% in the control group. In the risk pattern there were risks for neurological diseases, arterial hypertension, coronary heart disease, borderline mental disorders, and endocrine diseases.     

Some psychological characteristics of persons exposed to small-dose methylated mercury

In the area polluted by the man-caused mercury in the Angara River reservoir, there is fish accumulation of the toxic substance in the quantities exceeding the standard values by 2-4 times. The psychological characteristics of the persons exposed to mercury load due to fish ingestion were studied. A screening survey revealed the high situational and personality anxiety in 33.9 +/- 6.2 and 53.9 +/- 6.2% of the examinees, respectively. Lower logical and abstract thinking abilities were observed in 92.7 +/- 2.8% of the respondents. Poorer attention, significant fatiguability, and distraction were seen. According to the level of mercury in the biosubstrates, a risk group (n = 26) was formed, which was examined in the inpatient setting. The high prevalence of emotional instability and neurotism was revealed. When examined by a psychiatrist, 9 persons were recognized as apparently healthy. It is necessary to continue studies to objectivize the conclusion that small-dose methylmercury affects mental health.     

Transfer of cadmium in a phytoplankton-oyster-mouse food chain

The trophic transfer of cadmium (Cd) was studied in a phytoplankton-oyster-mouse food chain. Phytoplankton, grown in a continuous culture chemostat system containing CdCl₂ plus the isotope¹⁰⁹Cd, accumulated 70% of the total supplied cadmium. Oysters filtered out 85 to 95% of the phytoplankton. The rate of oyster Cd accumulation at 15 C increased linearly with seawater Cd concentration according to: y=0.066X – 0.15 (n =12, r=0.96); where X=g Cd/L seawater (between 2 and 22) and y=g Cd/g dry wt oyster/ day. About 59% of the Cd accumulated by the oysters came from the phytoplankton food source and 41% from the cadmium dissolved in the water. Sixty-one percent of the total supplied cadmium was retained in the whole soft body of the osyters. Mice fed 0.4 g of oyster-bound Cd per g of diet, retained 0.83% of the dietary cadmium consumed. Mouse kidney retention for organic oyster-bound cadmium was 0.14%. Extrapolation of these results to human risk assessment indicates that moderate consumption of oysters, which are not highly contaminated with cadmium, poses no significant health risk in terms of elevating kidney cadmium levels.     

Xenobiotics in the food chain

The problem of xenobiotics is presented by nitrate, cadmium, DDT and PCBs. Data are given especially for vegetables, supplemented by residue determinations in human breast milk.     

Accumulation of cadmium in a freshwater food chain experimental model

The study of food chain contamination in nature or in the laboratory requires precise definitions of some terms. A simplified model of a freshwater food chain has been elaborated to try to point out hazards related to the presence of cadmium in the aquatic environment. Three different species belonging to various trophic levels, but to the same aquatic systems were used. The required biological and analytical criteria are described. The time course of the experiment was 34 days starting with a 10-day contamination of the first trophic level (algae). The algae were then separated, washed with fresh medium, and given to the second trophic level (daphnids) to eat for 20 days. The third trophic level (fish) was then introduced for 4 days as a scavenger. The methodology was designed to determine the accumulation of cadmium by daphnids and then fish from the algal source. The results show a high direct bioaccumulation of cadmium in algae. The indirect bioaccumulation of daphnids was of the same order of magnitude, but for fish it was smaller. Nevertheless the cadmium transfer from daphnids to fish was obvious.     

直接测汞法在各类型食品分析中的应用研究

目的：使用直接测汞仪测定食品汞,掌握不同种类食品的测定条件。方法：将各种食品置于镍或石英样品舟中,在100℃～300℃进行干燥及预炭化,800℃～950℃灰化,汞经金齐化管富集,样品分解完成后瞬间加热破坏汞齐,汞蒸气进入比色池,直接测定样品中汞的含量,分析操作采用仪器全程控制。通过分析标准样品来考察方法准确性、精密度及适用性。结果：两种标准物质的汞测定值均在给定值范围内,CV分别为3.2%和5.4%。连续4个月采用直接测定法检测某固体胶囊型保健食品,测定结果均值8.47～8.56μg/kg（n=6）,CV为2.2%～3.9%（n=6）。结论：该方法准确度和精密度高,检测限可达0.01 ng。与国家标准方法（GB/T5990.17-2003）比较,解决了样品前处理过程中的损失问题,大幅缩短了食品中汞的分析周期,在食物中毒等公共卫生突发事件的检测中具有良好的应用前景。     

我国部分地区食品中汞含量的调查

１９９２年对我国六大类食品中的汞含量进行了调查，采集在北京、上海、江苏、四川和广东地区市场供应食品共５０５件，调查结果表明，粮食合格率为８８．５％，蔬菜合格率为９６．６％，肉、鱼、蛋和奶的合格率均达１００％。     

Intercomparison and applicability of some dynamic and equilibrium approaches to determine methylated mercury species in pore water

To assess adequately the impact of methylmercury (MeHg) on sensitive wetland ecosystems, accurate measurements of MeHg in pore water are required. In the present study, the feasibility of three methods for porewater sampling was investigated with respect to MeHg in sediments and rice paddy fields. The performance of dialysis samplers (peepers), sediment core sectioning followed by porewater separation by centrifugation (core), and the thin film diffusive samplers (DGT) were evaluated. These methods were intercompared in field experiments at two sites in Guizhou province, SW China disparately impacted by mercury pollution. All the methods report that the concentrations of MeHg in the soils of the Gouxi (GX) rice paddy near Wanshan were much higher than that in the sediment of the Hongjiadu Reservoir (HR), which is located within the Wujiang River basin. The three methods also report different MeHg profiles at the same site. However, these methods exhibit different temporal and spatial resolution scales, due to the differing operations involved with the sampling methods, may also reflect different states of MeHg in pore water. This corresponds to MeHg derived from diffusive flux, equilibrium concentration, and bulk concentration in pore water detected by DGT, peeper, and sediment core, respectively. The advantages and limits of the three methods are also presented.     

Antimicrobial-resistant campylobacter in the food chain in Mexico

Abstract We describe prevalence and antimicrobial susceptibility results for thermophilic Campylobacter isolates collected from humans, food, and food-animals in an integrated food chain surveillance network in Mexico. From 2003 to 2006, stool samples were collected from children with diarrhea at state sentinel hospitals. Concurrently, fecal samples from asymptomatic children in kindergartens, as well as raw chicken, pork and beef from retail outlets, and food-animal intestines from slaughterhouses were all collected in 65 cities from four different states. C. jejuni was identified with a standardized hippurate test. Hippurate negative, indoxyl acetate positive isolates were classified as Campylobacter spp. Susceptibility testing was performed by agar dilution according to Clinical and Laboratory Standards Institute guidelines. A total of 1,259 C. jejuni and 1,797 Campylobacter spp. isolates were recovered from 11,811 samples. Chicken was significantly more contaminated for both intestinal samples (93.6%) and meat products (58.3%), compared with swine (71.4%)/pork (14.6%) samples, and cattle (25.1%)/beef (5.3%) samples (p<0.001). Campylobacter was recovered from 5.1% of children with diarrhea and from 3.2% of asymptomatic children. Chicken was significantly more likely to harbor ciprofloxacin-resistant C. jejuni (85.8%) than swine (62.5%, OR=3.6), cattle (39.8%, OR=9.3), or humans (58.2%, OR=4.4). No significant differences were found for ciprofloxacin-resistant Campylobacter spp. among food-animals, but the rate in food-animals was significantly higher than in humans (84% vs. 56.7%, OR=4.0). Swine was significantly more likely to harbor erythromycin-resistant C. jejuni (14.8%) than chicken (3.5%, OR=4.9), cattle (1.8%, OR=9.3), or humans (3.0%, OR=5.7), and was associated with higher rates of erythromycin-resistant Campylobacter spp. (41.9%) than chicken (10.5%, OR=6.1) and humans (11.9%, OR=5.3). The high resistance rates to ciprofloxacin preclude the use of fluoroquinolones for treatment of campylobacteriosis in Mexico. Our results emphasize the need for ongoing and integrated surveillance of antimicrobial usage and antimicrobial susceptibility in humans and animals.     

Review of food policy and consumer issues of mercury in fish

Public health messages regarding seafood consumption are confounded by long standing dietary advice promoting the healthfulness of consuming fish and recent warnings concerning dangerous mercury levels in specified fish. The warnings vary by federal agency and are directed to vulnerable subpopulations, notably women of childbearing age, pregnant women, nursing mothers and young children. The issue of mercury in fish has received considerable media coverage, attention from consumer organizations and public policy review. The net result is an area of seemingly contradictory advice directed to consumers and health professionals on the type and quantity of fish safe to consume. This message that fish is nutritious and healthy is particularly understood by educated and affluent subpopulations who can afford a variety of fish in their diet. This review addresses the contradictory rhetoric and reviews the state and federal agency policy positions. It considers the arguments for and against disclosing mercury-related information and its anticipated impact on the extended health benefits of fish consumption versus the risk to vulnerable subpopulations. The issue of balancing and targeting healthy messages and dietary warnings on fish is important because within the U.S. childbearing population, it is conservatively estimated that 250,000 women may be exposing their fetuses to higher levels of methylmercury than is in federal public health guidelines; two million more may not be consuming enough low-mercury fish.