Arthur D. McKenzie

Dietary intakes of lead, cadmium, arsenic and fluoride by Canadian adults: a 24-hour duplicate diet study.

Twenty-four hour duplicate diets, including drinking water and snacks, were collected from 24 adults living in five Canadian cities. Each diet was separated by the participants into 10 food categories, and each of the samples was analyzed in duplicate for lead, cadmium, arsenic and fluoride. Minimum detection limits for the respective elements in foods were about 0.1, 0.01, 0.3 and 5 ng/g. Mean dietary intakes were 53.8 micrograms/day or 0.80 micrograms/kg/day for lead, 13.8 micrograms/day or 0.21 micrograms/kg/day for cadmium, and 16.7 micrograms/day or 0.26 micrograms/kg/day for arsenic. The median intakes were 42.7 micrograms/day or 0.57 mu/kg/day for lead, 11.9 micrograms/day or 0.17 micrograms/kg/day for cadmium, and 9.79 micrograms/day or 0.139 micrograms/kg/day for arsenic. Half of the participants lived in communities with 1 microgram/g fluoride in the drinking water, and half lived in cities with less than 0.2 microgram/g fluoride in the water. The dietary intake of fluoride for the former was 2802 micrograms/day or 39.7 micrograms/kg/day; while that of the latter was 563 micrograms/day or 8.5 micrograms/kg/day. The respective median intakes of fluoride were 2090 micrograms/day or 30.3 micrograms/kg/day, and 414 micrograms/day or 7.0 micrograms/kg/day. Contribution of individual foods and food categories to the dietary intakes is discussed.

Survey of total mercury in some edible fish and shellfish species collected in Canada in 2002

Total mercury was measured in the edible portions of 244 selected fish and shellfish purchased in Canada at the retail level. By species, average mercury concentrations ranged from 0.011 μg g−1 for oysters to 1.82 μg g−1 for swordfish. The predatory fish contained the highest concentrations of mercury: swordfish (mean 1.82 μg g−1, range 0.40–3.85 μg g−1), marlin (1.43, 0.34–3.19 μg g−1), shark (1.26, 0.087–2.73 μg g−1), and canned, fresh and frozen tuna (0.35, 0.020–2.12 μg g−1). Levels of mercury in the fresh and frozen tuna contained a mean of 0.93 μg g−1 (range 0.077–2.12 μg g−1) and were substantially higher than in the canned tuna (0.15, 0.02–0.59 μg g−1). In the canned tuna, mercury concentrations varied with subspecies, with the highest average concentrations being found in Albacore tuna (mean 0.26 μg g−1, range 0.19–0.38 μg g−1) and the lowest (0.047, 0.025–0.069 μg g−1) in five samples for which the subspecies of tuna were not identified. Mean concentrations of mercury in swordfish and fresh and frozen tuna were up to three times higher than reported for the USA. Dietary intake estimations found that provided fresh and frozen tuna, marlin, swordfish or shark are consumed once a month or less, the dietary intakes of total mercury by women of child-bearing age, averaged over 1 month, would fall below the Joint FAO/WHO Expert Committee on Food Additives provisional tolerable weekly intake for total mercury. The current Canadian advisory to children and women of child-bearing age is to limit their consumption of fresh and frozen tuna, swordfish and shark to no more than one meal per month.

Survey of bottled drinking waters sold in Canada for chlorate, bromide, bromate, lead, cadmium and other trace elements

Mineral, spring and other bottled drinking waters sold in Canada in the winter of 1995–96 were surveyed for chlorate, bromide, bromate, Cr(VI), Li, B, Al, Mn, Cu, Zn, Sr, Ba, Be, V, Cr, Co, Ni, As, Se, Mo, Ag, Cd, Sb, Tl, Pb, Na, K, Ca and Mg. Chlorate and bromide were determined by ion chromatography (IC) with conductivity detection, Cr(VI) by IC with colorimetric detection, bromate by solvent extraction and gas chromatography (GC), trace elements by inductively coupled plasma mass spectrometry (ICPMS), and Na, K, Ca and Mg by flame atomic absorption spectrometry (FAA). Most chemicals in the 199 samples analysed were well within national and international drinking water guidelines. World Health Organization and/or Canadian drinking water guidelines were exceeded for B (22 samples), Al (9), Cr (1), Mn (5), Ni (1), As (10), Se (24) and Pb (1). Bromate levels are reported for information purposes and are considered as the maximum concentrations in the samples. In three distilled water products, unexpectedly high concentrations of Cu (88-147 μg l-1) and Ni (16-35 μg l-1) were found, and a comparison of distilled and non-distilled waters from two of the brands suggested the likely cause to be contamination during the distillation process. Li concentration in one sample was at a therapeutic dose and could pose an overdose risk to individuals on Li medication.

Methylmercury levels in predatory fish species marketed in Canada

Mercury was detected in all analysed samples of swordfish, marlin, shark and tuna purchased from major supermarket outlets and fish retailers in three cities across Canada. Total mercury and methylmercury levels ranged up to 3845 and 2346 ng g−1, respectively. Swordfish contained the highest levels, followed by shark, fresh/frozen tuna and marlin. Levels in canned tuna were considerably less than the other examined samples. Methylmercury was extracted with toluene from enzymatically hydrolysed samples after the addition of sulphuric acid and potassium bromide. An L-cysteine back-extraction was used to separate the methylmercury from most organic co-extractives. Analysis of methylmercury (as methylmercury bromide) was by gas chromatography with pulsed discharge detection.

Survey of total mercury in total diet food composites and an estimation of the dietary intake of mercury by adults and children from two Canadian cities, 1998-2000.

Total mercury was measured in 259 total diet food composites from two Canadian cities. Levels were generally low, with 46% of the composites having concentrations below the limit of detection, which ranged from 0.026 to 0.506 ng g−1. The fish category contained the highest mercury concentrations, which averaged 67 ng g−1 and ranged from 24 to 148 ng g−1. All composites were below the Canadian guideline for total mercury in fish of 0.5 ppm. Dietary intakes of mercury averaged 0.022 µg kg−1 body weight/day (µg kg−1 day−1), and ranged from 0.012 µg kg−1 day−1 for females over 65 years old to 0.062 µg kg−1 day−1 for 0–1-month-old infants. For fish consumers, fish contributed to more than half of the ingested mercury. All intakes were well below Joint FAO/WHO Expert Committee on Food Additives Provisional Tolerable Weekly Intakes, expressed on a daily basis, of 0.71 µg kg−1 day−1 total mercury and 0.47 µg kg−1 day−1 methyl mercury, and also below a recent Health Canada recommended maximum methyl mercury intake of 0.2 µg kg−1 day−1 for children and women of child-bearing age.

Lead and cadmium levels in commercial infant foods and dietary intake by infants 0-1 year old.

Lead and cadmium levels were determined in 131 infant foods. Mean lead and cadmium levels were 19.3 and 3.3 ng/g for meats, 8.4 and 4.1 ng/g for vegetables, 14.9 and 0.58 ng/g for fruits and desserts, 9.6 and 0.53 ng/g for juices and drinks, and 32.8 and 33.6 ng/g for dry infant cereals. These data, combined with those from other recent surveys, yielded average dietary (food and water) intakes of lead and cadmium by infants 0-1 year old of 2.4 and 0.37 microgram/kg/day, respectively. Lead intakes were most strongly influenced by storage of infant formulas in lead-soldered cans. For infants 0-1 month old, they ranged from 0.5 microgram/kg/day when human or cow milk was fed to infants to 5.3 micrograms/kg/day (exceeding the FAO/WHO provisional tolerable daily intake, PTWI, of lead by children of 3.5 micrograms/kg) when ready-to-use formula stored in lead-soldered cans was fed. Cadmium intakes were most strongly affected by soya based formulas, and ranged, for 0-1 months olds, from 0.16 microgram/kg/day for infants fed human or cow milk to 0.50 microgram/kg/day for infants fed soya-based concentrated liquid formula. Cadmium intakes were all below the FAO/WHO PTDI of cadmium by adults of 0.96-1.2 micrograms/kg.

Lead contamination of raisins sold in Canada.

Graphite-furnace atomic absorption spectrometric analysis of raisins imported in 1993–95 from different countries into Canada showed that raisins from Turkey had unusually high lead levels. The Turkish raisins (n = 18) contained a mean (range) of 0.93 (0.056–3.1)mg kg -1 lead, whereas five samples from Australia, South Africa, Iran, Mexico and Chile contained a mean of 0.0085 (0.005–0.010)mg kg-1. Acid-washing studies showed that most of the lead in the Turkish raisins was on the surface of the fruit. The impact of eating the raisins on the dietary intake of lead was estimated for Canadians of different ages and sexes. For example, eating raisins from Turkey would increase the dietary intake of lead by 1–4-year-old children from 0.97 to ∼2.2 μg kg-1 body weightday-1. The source of the lead was traced to use of a copper fungicide contaminated with high lead levels. Currently, lead levels in raisins imported from Turkey are low and approach levels in raisins from other countries. Uncontaminated raisins contain ∼0.01mg lead kg-1, and a maximum tolerance for lead in raisins of 0.1mg kg-1 is achievable irrespective of the type of raisin or country of origin. Therefore, consideration should be given to proposing this level as a maximum tolerance for lead in raisins.

Total mercury in canned tuna sold in Canada in 2006

Total mercury was measured in 156 composites prepared from 936 samples of canned tuna sold in Canada in 2006. Each composite comprised a single brand. Yellowfin tuna contained the lowest concentrations, averaging 0.066 mg/kg. Skipjack tuna contained slightly higher concentrations, averaging 0.132 mg/kg. The highest average concentration was found in the Albacore tuna: mean 0.325 mg/kg, range 0.174–0.507 mg/kg. The second highest concentration among the 49 albacore composites was 0.469 mg/kg. There were 72 composites for which the type of tuna was not specified. The mercury in these averaged 0.095 mg/kg and ranged from 0.016 to 0.237 mg/kg.

Levels of total mercury in predatory fish sold in Canada in 2005

Total mercury was analysed in 188 samples of predatory fish purchased at the retail level in Canada in 2005. The average concentrations (ng g−1, range) were: sea bass 329 (38–1367), red snapper 148 (36–431), orange roughy 543 (279–974), fresh water trout 55 (20–430), grouper 360 (8–1060), black cod 284 (71–651), Arctic char 37 (28–54), king fish 440 (42–923), tilefish 601 (79–1164) and marlin 854 (125–2346). The Canadian standard for maximum total mercury allowed in the edible portions of fish sold at the retail level is 1000 ng g−1 for shark, swordfish, marlin, orange roughy, escolar and both fresh and frozen tuna. The standard is 500 ng g−1 for all other types of fish. In this study, despite the small number of samples of each species, the 1000 ng g−1 maximum was exceeded in five samples of marlin (28%). The 500 ng g−1 maximum was exceeded by six samples of sea bass (20%), four of tilefish (50%), five of grouper (24%), six of king fish (40%) and one of black cod (13%),

Survey of total mercury in infant formulae and oral electrolytes sold in Canada

Total mercury (Hg) was measured in 150 infant formula products (as sold) and oral electrolyte solutions purchased in Canada in 2003. Results less than the limit of detection (LOD) were reported as the numeric value of the LOD. Electrolytes contained the lowest concentrations, averaging 0.026 ng/g. Average levels in milk-based ready-to-use, concentrated liquid and powdered concentrate were 0.028, 0.069 and 0.212 ng/g, respectively. In soy-based formulae, the respective mean concentrations were 0.049, 0.101 and 0.237 ng/g. These concentrations cannot be considered on an absolute basis because 76% of sample concentrations fell below the limit of detection. Despite the inability to measure many of the actual background concentrations, the method was sufficiently sensitive to identify clear cases of low-level Hg contamination (up to 1.5 ng/g) of individual lots of powdered formula. Also, all the different lots of one brand of concentrated liquid infant formulae had significantly higher concentrations of Hg than those of all other concentrated liquid products. After dilution with preparation water, the Hg concentrations in all products would be lower than the Canadian Drinking Water Guideline for Hg of 1 ng/mL and too low to impact on health.