Mercury dietary exposure

Gariboldi, J.C., C.H. Jagoe, and A.L. Bryan Jr. 1998. Dietary exposure to mercury in nestling wood storks (.Mycteria americana) in Georgia. Arch. Environ. Contam. Toxicol. 34 398-405. 

This chapter reviewed current research pertaining to selected environmental agents and autoimmune diseases (Table 25.3). Other infectious agents (e.g., parvovirus, varicella), occupational exposures (e.g., mercury), dietary factors (dietary supplements, nutrients such as antioxidants, and specific proteins in wheat and other grains implicated in celiac disease), and stress have been the focus of additional research that was not included in this review. 

Investigations into the presence of mercury in food have been carried out in a comparatively small number of foods in the UK since 1966. Mercury is included in the analytes measured in the samples of the Total Diet Study. The estimated dietary exposures to total mercury (organic and inorganic) for the general population as determined from the UK TDS (Table 7.5) have remained fairly constant between 0.002 and 0.005 mg/day. The dietary exposures of mean and 97.5th percentile consumers in the UK in 1997 were 0.0031 mg/day and 0.0064mg/day.10 These may be compared with the JECFA PTWI for mercury of 0.005 mg/kg bodyweight/week (of which no more than two-thirds should be methyl mercury),31 which is equivalent to 0.043 mg/day for a 60 kg adult. The dietary exposures are similar to those in the USA (0.008 mg/day)8 and the Netherlands (0.002 mg/day)7 but lower than New Zealand (0.013 mg/day).18... 

The highest concentrations of mercury are found in the fish group of the TDS, which contributes about 33% to the overall dietary exposure. Higher than usual concentrations of mercury can sometimes be found in the cereals and the meat groups, which indicates that contamination of these foods can occur. 

Table 7.5 Population dietary exposures to mercury from UK Total Diet Studies (mg/ day)...

YSART G E, MILLER P F, CREWS H, ROBB P, BAXTER M, DE L ARGY C, lofthouse s, sargent c and Harrison N, 1997 UK total diet study -dietary exposures to aluminium, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, tin and zinc, Food Additives and Contaminants, 2000 17 775-86. 

Chung, S.W.C., Kwong, K.P., Yau, J.C.W., Wong, W.W.K. Dietary exposure to antimony, lead and mercury of secondary school students in Hong Kong. Food Addit. Contam. 25, 831-840 (2008)... 

The only study located regarding respiratory effects in animals after oral exposure to inorganic mercury described forceful and labored breathing, bleeding from the nose, and other unspecified respiratory difficulties in Long-Evans rats after dietary exposure to 2.2 mg Hg/kg/day as mercuric chloride for 3 months (Goldman and Blackburn 1979). 

Exposure pathways for adult amphibians include soils (dermal contact, liquid water uptake), water (dermal contact with surface water), air (cutaneous and lung absorption), and diet (adults are carnivores). All routes of exposure are affected by various physical, chemical, and other factors. Dietary exposure in adults, for example, is related to season of year, activity rates, food availability, consumption rate, and assimilation rates. Knowledge of these modifiers is necessary for adequate risk assessment of mercury as a possible factor in declining amphibian populations worldwide. 

Dietary exposure of amphibians in sites receiving mercury mainly via atmospheric deposition - estimated to range from 1.5 to 3.0 mg Hg/kg FW ration - may be sufficient to adversely affect survival, growth, and development. Studies with tadpoles of the southern leopard frog (Rana sphenocephala) fed mercury-containing diets for 254 days showed that about 28% died at the highest concentrations fed of 0.5 and 1.0 mg Hg +/kg FW ration malformation rates were dose-related, with 5.0% in controls, 5.6% in the 0.1 mg Hg/kg FW diet, 11.1% in the 0.5mg/kg and 27.8% in the l.Omg/kg diet. Malformations included dose-related scoliosis. Arrested growth and development, and tail resorption were also positively dose-related. Total mercury body burdens were also dose-related with about... 

Exposure. The exposure of humans and animals to mercury from the general environment occurs mainly by inhalation and ingestion of terrestrial and aquatic food chain items. Pish generally rank the highest (10—300 ng/g) in food chain concentrations of mercury. Swordfish and pike may frequently exceed 1 p.g/g (27). Most of the mercury in fish is methyl mercury [593-74-8]. Worldwide, the estimated average intake of total dietary mercury is 5—10 p-g/d in Europe, Russia, and Canada, 20 pg/d in the United States, and 40—80 pg/d in Japan (27). 

Ponce RA, BarteU SM, Kavanagh TJ, Woods JS, Griffith WC, Lee RC, Takaro TK, Faustman EM. 1998. Uncertainty analysis methods for comparing predictive models and biomarkers a case study of dietary methyl mercury exposure. Regulatory Toxicol Pharmacol 28 96-105. 

The main sources of exposure to mercury for the general population are from the diet and dental amalgam.21,28 The main dietary source of mercury is fish and this has led to interest in potential exposure to mercury on the neurological development of children from populations with high fish consumption.29 There is no statutory control of mercury in most food in the UK, but the levels of mercury in fish are controlled by European Commission Decision 93/351/EEC which sets an average limit for mercury in fish of 0.5 mg/kg or 0.5 ppm (part per million).30 This average limit is, however, increased to 1.0 mg/kg or 1 ppm for the edible parts of the predatory and bottom-dwelling species listed in the Annex to the Decision. 

Besides dietary and dental amalgam exposure to mercury compounds, accidental exposure to mercury vapors may occur among the general population (e.g., from breakage of a mercury-containing thermometer), or from use of metallic mercury or mercury containing ointments, creams, and drugs. 

Potential sources of human exposure to mercury include food contaminated with mercury, inhalation of mercury vapors in ambient air, and exposure to mercury through water, soil and sediment. Dietary intake is by far the most important source of exposure to mercury for the general population. Fish and other seafood products are the main source of methylmercury in the diet studies have shown that methylmercury concentrations in fish and shellfish are 10-100 times greater than in other foods, including cereals, potatoes, vegetables, fruits, meats, poultry, eggs, and milk. As of December 1998, mercury was the chemical contaminant responsible, at least in part, for the issuance of 1931 fish consumption advisories by 40 states, including the US territory of American Samoa. Almost 68% of all advisories issued in the United States are a result of mercury contamination in fish and shellfish. Advisories for mercury have increased steadily by 115% from 899 advisories in 1993 to 1931 advisories in 1998. The number of states that have issued mercury advisories also has risen steadily from 27 states in 1993 to 40 states in 1997, and remains at 40 states for 1998. Advisories for mercury increased nearly 8% from 1997 (1782 advisories) to 1998 (1931 advisories). 

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