Chemical contaminant levels in edible seaweeds of the Salish Sea and implications for their consumption

Abstract

Despite growing interest in edible seaweeds, there is limited information on seaweed chemical contaminant levels in the Salish Sea. Without this knowledge, health-based consumption advisories can not be determined for consumers that include Tribes and First Nations, Asian and Pacific Islander community members, and recreational harvesters. We measured contaminant concentrations in edible seaweeds (Fucus distichus, F. spiralis, and Nereocystis luetkeana) from 43 locations in the Salish Sea. Metals were analyzed in all samples, and 94 persistent organic pollutants (POPs) (i.e. 40 PCBs, 15 PBDEs, 17 PCDD/Fs, and 22 organochlorine pesticides) and 51 PAHs were analyzed in Fucus spp. We compared concentrations of contaminants to human health-based screening levels calculated from the USEPA and to international limits. We then worked with six focal contaminants that either exceeded screening levels or international limits (Cd, total Hg, Pb, benzo[a]pyrene [BaP], and PCBs) or are of regional interest (total As). USEPA cancer-based screening levels were exceeded in 30 samples for the PCBs and two samples for BaP. Cadmium concentrations did not exceed the USEPA noncancer-based screening level but did exceed international limits at all sites. Lead exceeded international limits at three sites. Because there are no screening levels for total Hg and total As, and to be conservative, we made comparisons to methyl Hg and inorganic As screening levels. All samples were below the methyl Hg and above the inorganic As screening levels. Without knowledge of the As speciation, we cannot assess the health risk associated with the As. While seaweed was the focus, we did not consider contaminant exposure from consuming other foods. Other chemicals, such as contaminants of emerging concern (e.g., PFAS, pharmaceuticals and personal care products), should also be considered. Additionally, although we focused on toxicological aspects, there are cultural and health benefits of seaweed use that may affect consumer choice.

Evidence of elevated heavy metals concentrations in wild and farmed sugar kelp (Saccharina latissima) in New England

“…The baseline analysis of ecotoxicological kelp data that we’ve presented here highlights that, in New England, total arsenic and cadmium are often found at levels that would not meet food safety standards—both in wild and farmed sugar kelp. Our results and commensurate recommendations generally align with other research on edible seaweeds 20 , 24 , 26 , 27 , 43 , 46 and suggest that longline-grown sugar kelp is subject to the same contaminant concentrations as wild populations. Until now, heavy metals analysis at this level of detail has not been available for Northeastern US populations, particularly for multiple locations along sugar kelp blades.…”

“…As summarized in their review, the EU establishes maximum contaminant limits (MCLs) for heavy metals concentrations in seaweeds used in animal feed and food supplements (see Table 2 and citations therein). The EU’s available standards are often referenced by researchers in the US as a starting point for those seeking to design domestic guidance 20 , 43 . In terms of relevant US regulations, some farmers address California’s Proposition 65 Safe Harbor level standards on their websites and in outreach efforts 44 (e.g., Maine Coast Sea Vegetables ).…”

“…One reason for this gap in knowledge is that few organizations or individuals have the directive or resources necessary to evaluate contaminants in seaweed 6 , 19 , 27 ; testing is expensive and requires expertise and equipment rarely possessed by members of the seaweed farming community. However, using the EU standards mentioned above (also see Table 2 ), researchers have indeed detected heavy metals concentrations of concern in edible seaweed sold in Spain 25 , 46 , Italy 27 , the U.K. 47 , 48 , South Korea 23 , and the Salish Sea 20 .…”

“…In terms of risks, seaweed's ability to assimilate compounds from its surrounding environment can also present a challenge for farmers and give rise to a risk to consumers. Brown seaweeds such as sugar kelp are known accumulators of heavy metals [17][18][19][20] .…”

Arctic Edible Brown Alga Fucus distichus L.: Biochemical Composition, Antiradical Potential and Human Health Risk

“…In previous publications, the promising antioxidant potential of F. distichus was associated with I ts high phlorotannin content [ 11 ]. Brown seaweeds, like F. distichus are known for their enhanced capacity for the accumulation of minerals and organic and inorganic contaminants from sediments and seawater due to their unique structural and physiological characteristics [ 22 , 23 , 24 , 25 ]. Consuming edible seaweed regularly could result in increased health hazards due to its capacity to accumulate elements.…”