Food and Chemical Toxicology 60 (2013) 205–212
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Evaluation of dietary exposure to minerals, trace elements and heavy metals from the muscle tissue of the lionfish Pterois volitans (Linnaeus 1758) Leslie A. Hoo Fung a, Johann M.R. Antoine a,⇑, Charles N. Grant a, Dayne St. A. Buddo b a b
International Centre for Environmental and Nuclear Sciences, University of The West Indies, 2 Anguilla Close, Mona, Kingston 7, Jamaica Centre for Marine Sciences, Discovery Bay Marine Laboratory, University of The West Indies, Mona, Kingston 7, Jamaica
a r t i c l e
i n f o
Article history: Received 10 April 2013 Accepted 17 July 2013 Available online 26 July 2013 Keywords: Lionfish Jamaica Dietary exposure Trace elements Food safety Heavy metals
a b s t r a c t Twenty-five samples of Pterois volitans caught in Jamaican waters were analyzed for 25 essential, non-essential and toxic elements using Graphite Furnace Atomic Absorption Spectrophotometry (GF-AAS), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Instrumental Neutron Activation Analysis (INAA). The mean values for calcium (355 mg/kg), copper (107 lg/kg), iron (0.81 mg/kg), potassium (3481 mg/kg), magnesium (322 mg/kg), manganese (0.04 mg/kg), selenium (0.47 mg/kg), sodium (700 mg/kg) and zinc (4.46 mg/kg) were used to estimate dietary intake. The percentage contribution to provisional tolerable weekly intake for a 70 kg male and a 65 kg female were also estimated for the toxic elements arsenic (1.28% M, 1.38% F), cadmium (0.26% M. 0.28% F), mercury (3.85% M, 4.15% F) and lead (0.17% M, 0.18% F). To further assess the risk of mercury toxicity and the role of mitigation provided by selenium, selenium-mercury molar ratios were calculated for all samples. All samples were shown to have a molar excess of selenium. In addition the suggested selenium health benefit value was calculated, and was positive for all samples. It was concluded that P. volitans appears to contribute modestly to mineral and trace element nutrition, while not being a significant contributor to dietary exposure of toxic elements. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction The successful colonization of the north-western Atlantic Ocean and the Caribbean Sea by the non-native lionfish species Pterois volitans is of significant concern to a number of sectors. Not only is this the first invasive marine species to successfully establish itself in this geographic region, Jamaica included, (Schofield, 2009) but it has been described as one of the most rapid invasions by a marine finfish in history (Morris et al., 2009). Evidence has already risen of the negative effect that the presence of these fish may have on the native coral reef fish. Observations over a 5 week period showed an almost 80% reduction in the recruitment of native coral reef fish in the Atlantic due to the presence of this invasive species (Albins and Hixon, 2008). Further investigations have led to predicted scenarios where lionfish predation could eventually decimate the native fish stock and the consequential deleterious effects that could follow (Albins and Hixon, 2011). Strategies for the control and mitigation of the lionfish invasion have been suggested (Mumby et al., 2011), however the initial primary strategy of control in Jamaican waters has been a campaign ⇑ Corresponding author. Tel.: +1 (876) 935 8532 3; fax: +1 (876) 977 0768. E-mail address:
[email protected] (J.M.R. Antoine). 0278-6915/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fct.2013.07.044
to consume lionfish dubbed, ‘‘Eat them, to beat them’’ thereby introducing lionfish to the local diet. This strategy is not unique to Jamaica and P. volitans is now consumed in America, Mexico and several Caribbean islands (PBS, 2013; Jamaica Gleaner, 2012; Inter Press, 2012). Fish is considered highly nutritious because of its high protein content and low levels of saturated fat as well as the purported benefits of omega 3-fatty acids (Yildirim et al., 2009). Fish however, can also be a source of contamination due to the potential for bioaccumulation of several elements particularly heavy metals, through trophic system interactions and to a lesser extent direct contact with the environment (Rejomon et al., 2010). For example, it is well accepted that fish and seafood are the major source of dietary exposure to methyl mercury (EFSA, 2004). With the introduction of lionfish into the North American, Central American and Caribbean diet, an opportunity presented itself to assess an aspect of the nutritional safety of this relatively new food source at an early stage in its adoption. The objective of this study therefore, was to determine the essential and toxic elements in the muscle tissue of P. volitans. As the muscle is the main edible part of the fish, analysis of this tissue represents the best mechanism for the assessment of contributions to element nutrition and exposure to toxic elements. This study is particularly
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important for a population such as Jamaica who are already exposed to potentially toxic elements through diet because of the naturally enriched levels of arsenic, cadmium and mercury found in some soils (Lalor et al., 1999).
2. Methods and materials Whole fish samples were removed from selected sites around Jamaica. Sampling sites were located on the Southwest and Northern coasts of Jamaica (see Fig. 1). The sites were chosen based on high frequency of removals of lionfish by fishermen at these areas which are then consumed by humans on the local market. At each station, 20 fish were collected using stainless steel pole spears. The sample was sub-sampled to get a size range of 250–350 mm. A total of 25 fish were used in the assessment. These were put on ice immediately and then frozen until transported to the laboratory. Samples were thawed, cleaned and scaled, then filleted. The fillets were dried at 65 °C then ground to a fine powder in a Fritsch Pulverisette 2 automated agate mortar and pestle (Fritsch, Germany). Samples were prepared for Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis by acid digestion. 10 mL of HNO3 was added to 0.5 g of sample in an EasyPrep Teflon vial and allowed to stand for 1 h before digestion using a CEM MARS5 microwave system (CEM Corporation, NC, USA). After cooling, samples were made up to 25 mL using deionized water. Analyses were performed using a PerkinElmer Optima 7000DV ICP-OES (PerkinElmer, MA, USA). Calibration standards for ICP-OES analyses were prepared using Certiprep solutions (SPEX Certiprep, NJ, USA) in 2% HNO3. An internal standard containing 0.2 mg/L yttrium was also used. Acid digested samples were also analyzed by Graphite Furnace Atomic Absorption Spectrophotometry (GF-AAS) using a PerkinElmer AAnalyst600 Spectrophotometer (PerkinElmer, MA, USA) with Zeeman Background Correction. Calibration standards were prepared using Certiprep solutions (SPEX Certiprep, NJ, USA) in 2% HNO3. A matrix modifier (Ammonium Dihydrogen Phosphate + Magnesium Nitrate) was added to samples for all GF-AAS analyses. Instrumental Neutron Activation Analysis (INAA) was performed using the SLOWPOKE-2 nuclear reactor. For the determination of short-lived radioisotopes, approximately 0.5 g of sample was weighed out into pre-cleaned double polyethylene bags and heat sealed in pre-cleaned 7 cm3 polyethylene vials (Lalor et al., 2000). Each sample was irradiated for 3 min at a neutron flux of 5 1011 n cm2 s1 and allowed decay periods of approximately 5 and 60 min before counting. For intermediate and long lived radioisotopes approximately 1 g of sample was weighed out in pre-cleaned polyethylene capsules which were then heat sealed in 7 cm3 polyethylene vials and irradiated for 4 h at a neutron flux of 10 1011 n cm2 s1 and allowed decay periods of 4 days and 14 days respectively before counting. For short and intermediate-lived radioisotopes gamma ray spectroscopy was performed using an Ortec High-Purity germanium coaxial gamma photon detector system with an efficiency of 71% and a resolution of 1.8 keV at the 60Co 1332 keV gamma line. Long lived radioisotopes were counted on an EG&G Ortec High-Purity Germanium detector with an efficiency of 20% and a resolution of 1.9 keV at the 60Co 1332 keV gamma line. Cr, Fe, K, Mn, Na and Zn were determined using ICP-OES; Cd, Cu and Pb were determined by GF-AAS; and As, Ba, Br, Ca, Ce, Cs, Eu, Hg, La, Mg, Rb, Sc, Se, Sm, Sr and Th were determined using INAA.
2.1. Quality control Approximately 10% of the samples were analyzed in duplicate, with the differences between duplicates being less than 15%; at least one reagent blank and a certified reference material were also included in each analysis batch. Reference materials used were IRMM (Institute for Reference Materials and Measurements, Geel, Belgium) ERM-CE 278 – Mussel Tissue, IAEA (International Atomic Energy Agency, Vienna, Austria) 336 – Lichen, IAEA 436 – Tuna Fish Flesh and NIST (National Institute of Standards and Technology, MD, USA) 1547 – Peach Leaves. Recovery for srms was within acceptable limits of ±15%. SRM data are shown in Table 1. The linear range for elements analyzed using ICP-OES is low mg/kg to 103 mg/kg in the samples. The linear range for samples analyzed using GF-AAS is low lg/kg to low mg/kg in the samples. Digested samples which were beyond the linear range were diluted to fall within the linear range and reanalyzed. The linear range for INAA is low mg/kg to 104 mg/kg. Note that INAA detection limits may vary (Howe et al., 2005).
3. Results and discussion Jamaicans consume approximately 41.64 g daily of sea fish based on a marine fish (‘‘Other’’) supply quantity of 15.2 kg per person per year (FAOSTAT, 2009). This statistic was used to estimate dietary intake of essential elements as well as exposure to potentially toxic elements. Daily intake estimates were calculated using the formula:
Daily Intakeðmg=dayÞ ¼ mean concentration ðmg=kgÞ food supply quantity ðkg=dayÞ Several studies measure heavy metals and/or trace elements in various organs and tissues of fish and often find that muscle tissue has lower concentrations of trace elements than say the liver or gills (Wagner and Boman, 2003; Staniskiene et al., 2006; Yilmaz, 2009). In this study only the muscle was analyzed as this is the main edible tissue of fish. Analytical data are summarized in Table 2. All data are reported as wet weight. 3.1. Potentially toxic elements: As, Cd, Pb, Hg The total arsenic concentrations in lionfish muscle ranged from 1.12 mg/kg to 22.14 mg/kg wet weight, with a mean of 4.61 mg/kg. The second highest concentration was 9.53 mg/kg and 88% of the concentrations determined were under 5 mg/kg. The mean total arsenic in the muscle tissue of lionfish was higher than the mean concentrations of zinc and iron, both essential metals. Arsenobetaine is the most dominant form of arsenic in marine fish and most other seafood. This organoarsenical is regarded as being non-toxic
Fig. 1. Locations of sampling sites.
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L.A. Hoo Fung et al. / Food and Chemical Toxicology 60 (2013) 205–212 Table 1 Reference material data. Reference material
Element
Technique used
n
Analyzed value
Reference value
95% confidence intervalb
LOD
IRMM ERM CE-278 – Mussel Tissue
Cd Cr Cu Pb Se Zn
GF-AAS ICP-OES GF-AAS GF-AAS INAA ICP-OES
5 4 5 5 3 5
0.32 0.72 8.78 2.016 1.87 88.5
0.348 ± 0.007 0.78 ± 0.06 9.45 ± 0.13 2.00 ± 0.04 1.84 ± 0.10 83.1 ± 1.7
na na na na na na
0.004 0.023 0.017 0.014 0.031 0.050
IAEA 336 – Lichen
As Ce Cs Eu Sc Th
INAA INAA INAA INAA INAA INAA
1 1 1 1 1 1
0.64 1.3 0.097 0.02 0.17 0.14
0.63 1.28 0.11 0.023a 0.17a 0.14
0.55–0.71 1.11–1.45 0.097–0.123 0.019–0.027 0.15–0.19 0.12–0.16
0.020 0.036 0.002 0.001 0.000 0.003
IAEA 436 – Tuna Fish Flesh Homogenate
Br Fe Hg K Mg Mn Na Rb
INAA ICP-OES INAA ICP-OES INAA ICP-OES ICP-OES INAA
4 5 4 5 2 4 5 4
15.18 81.76 4.48 12,067 1098 0.22 1294 2.63
14.8a 89.3 4.19 12300a 1070 0.238 1501a 2.41a
10.9–18.6 87.8–90.9 4.04–4.34 11,500–13,000 1020–1110 0.218–0.257 1306–1696 1.96–2.86
0.020 0.241 0.014 7.65 45.5 0.013 137 0.042
NIST 1547 – Peach Leaves
Ba Ca La Sm Sr
INAA INAA INAA INAA INAA
1 1 1 1 1
108 15,438 8.244 0.904 46.9
124 ± 4 15,600 ± 200 9a 1a 53 ± 4
na na na na na
5.23 5.19 0.011 0.001 0.893
a
Non-certified value. It should be noted that the confidence interval for the reference value was calculated from the combination of the standard deviation of the mean value and an additional 5% to account for any variation due to sample inhomogeneity. b
and therefore of no nutritional concern (EFSA, 2010). Furthermore, no reports of toxicity as a result of the consumption of organoarsenicals, have been reported in humans or animals. Fish and seafood are regarded as the most significant sources of dietary exposure to total arsenic, but are typically very low in inorganic arsenic (Schoof et al., 1999; Budiati, 2010). In 2010 the Joint FAO/WHO Expert Committee on Food Additives (JECFA) lowered the provisional tolerable weekly intake (PTWI) of inorganic arsenic from 15 lg/kg of body weight to 3 lg/kg of body weight as evidence indicated cancer caused by this form of arsenic occurred at lower levels of exposure than the previous PTWI (JECFA, 2010). Schoof et al. (1999) showed total arsenic in marine fish ranging up to 2.4 mg/kg wet weight but that the average inorganic arsenic in these fish was between 0.001 and 0.002 mg/kg wet weight. Studies show a range of concentrations of inorganic arsenic in fish and seafood but collectively suggest the inorganic portion of total arsenic to be approximately 1% (Abernathy and Morgan, 2001). This study only determined total arsenic in the lionfish muscle tissue. The calculation of PTWI of inorganic arsenic based on total arsenic would result in an overestimation of the risk associated with dietary exposure to inorganic arsenic in seafood. Therefore, using the estimation of inorganic arsenic as 1% of total arsenic in fish and seafood it was determined that lionfish would contribute roughly 1.28% to the PTWI of a 70 kg male and 1.38% to a 65 kg female (see Table 3). Cadmium has never been shown to have any biological role in humans and is well known as a carcinogen and nephrotoxin (Hall and Shannon, 2007). Only one lionfish sample showed detectable cadmium of 8.70 lg/kg wet weight. The World Health Organization (WHO) has set the provisional tolerable weekly intake (PTWI) for cadmium at 7 lg/kg of body weight. If the entire consumption of sea fish was lionfish at the maximum detectable concentration of 8.70 lg/kg it would contribute only 0.52% and 0.56% to the PTWI of a 70 kg male and 65 kg female respectively.
Table 2 Concentrations of elements in lionfish. Element
Range
Mean ± SD
As (mg/kg) Ba (mg/kg) Br (mg/kg) Ca (mg/kg) Cd (lg/kg) Ce (mg/kg) Cr (mg/kg) Cs (mg/kg) Cu (lg/kg) Eu (mg/kg) Fe (mg/kg) Hg (mg/kg) K (mg/kg) La (mg/kg) Mg (mg/kg) Mn (mg/kg) Na (mg/kg) Pb (lg/kg) Rb (mg/kg) Sc (mg/kg) Se (mg/kg) Sm (mg/kg) Sr (mg/kg) Th (mg/kg) Zn (mg/kg)
1.12–22.1
