# Atomic Spectroscopy-Based Analysis of Heavy Metals in Seaweed Species
### Health Risks Associated with Seaweed Consumption  
Due to the toxicity of even trace amounts of heavy metals and other elements, eating large amounts of seaweeds that absorb pollutants may pose a health risk. High biosorption results in potentially harmful amounts of lead, mercury, inorganic arsenic, nickel, cadmium, and also toxic levels of the essential elements iodine, copper, and zinc [23; 24; 25]. Even if measurements of heavy metals in seawater or sediment seem not to be at levels sufficient to raise any concern, measurements in seaweed can possibly be thousands of times higher in the same environment [4; 5; 26]. The nonessential elements lead, cadmium, arsenic, and mercury have been specifically studied and are said to pose a carcinogenic risk [4]. Arsenic can be found in either organic or inorganic forms, with the latter being more toxic and dangerous to health. The similarity in the chemical structure of phosphate, an essential building block for DNA, and arsenate, which can interrupt DNA synthesis, causes both to be absorbed equally into seaweed, explaining why seaweed can also contain high levels of arsenic [23; 24]. Based on human toxicity data, local guidelines as well as international standards have been set for permissible levels of heavy metals in food and drinking water. Table 1 lists the permissible levels for the four heavy metals that are most hazardous to human health [27; 28; 29; 30; 31; 32; 33; 34; 35].  
Creating risk assessments based on regular surveys of heavy metal concentrations in commercially available seaweed is suggested to protect consumers and maintain food safety [36; 37; 38]. While the negative health effects of heavy metals on the body have been studied thoroughly, many studies have pointed out the need for more research on heavy metals or metalloids in seaweed, especially species-specific studies [23; 24; 25]. Lack of data on the distribution of metal contamination in waters and pre-/post-market seaweed in specific geographic areas, such as Europe and Malaysia, leaves the safety of consuming seaweed in question [3].  
The European Union has taken action to collect data and to potentially establish maximum allowable levels of elements in seaweed to prevent high exposure to toxins within the population [3; 24]. The European Union has also published a recommendation on monitoring specific trace elements in seaweeds that are intended for consumption [23].  
A study suggests limiting the consumption of seaweed and changing dietary habits due to the exposure risk of unhealthy trace metal levels [7]. More research on both the beneficial qualities and potentially harmful elements in specific seaweed species is needed to differentiate between environmental contamination and acceptable element levels [6; 24; 39]. One study focused on the species _Sargassum fusiforme_, also known as hijiki, a commonly eaten seaweed in Japan. While it is a popular seaweed to be eaten, if exposed to pollution, it is said to be likely to contain excessive amounts of heavy metals which are dangerous to the consumer. Even the essential elements copper, chromium, and zinc were found to be concentrated at toxic levels. Thus, detection models for specific elements in _Sargassum fusiforme_ are needed for quality assurance in the case of this popular product [25]. Several studies found that levels of nonessential elements found in seaweed were greater than acceptable concentration limits. Limits set by European regulations were exceeded by the lead concentrations of multiple seaweed species from a collecting site in the Mediterranean Sea, and the combined risk of nonessential element amounts in seaweed exceeded the United States Environmental Protection Agency reference limit of \(10^{-4}\), showing evidence of carcinogenic risk [1; 4]. The presence of antimony (a metalloid that can impair cellular metabolism), cobalt, and vanadium in seaweed has also been reported [39].