Lycium barbarum L. (Solanaceae), produces a fruit known as the Goji berry or wolfberry and has been used as a traditional Chinese medicine for centuries [1]. Goji berries are popular worldwide as a health food, and they are consumed in various forms, including soups, drinks, and in certain dishes [2] because of their potential beneficial effects. Goji berries are rich in compounds with positive biological activities, including polysaccharides, carotenoids, and flavonoids [3], and their consumption has been linked with health benefits, such as antioxidant [4], and anticancer [5] effects.
Goji berries are mostly cultivated in China. While, there is growing interest in Goji cultivation in other countries, for example, Italy, Greece, Poland, Romania [6]. In China, the mainly cultivated areas are in northwestern provinces of China, such as Ningxia, Qinghai, Xinjiang, and Inner Mongolia, and Zhongning County in Ningxia is the geographical origin of the Goji berry. The fruit is typically orange-red (although there are black–purple varieties in Qinghai province), has a sweet taste, and matures from late June to late September. Goji berries have high sugar content and are extremely hygroscopic. In addition, they are easily damaged by worms. To eliminate pests, farmers apply pesticides during Goji growth period. Thus, Goji berries could contain pesticide residues. In addition to pesticides, Goji berries absorb metals from cultivated soil. Further, some berries are fumigated to improve their appearance, and, thus, metals also introduced by this route. Consequently, pesticides and metals are the major hazardous chemicals in Goji berries. Previously, many types of pesticides and metals have been detected in Goji berries [7–8]. According to Chinese Pharmacopoeia (2015) [9], three pyrethroids and 12 organophosphates pesticides need to be detected in Chinese herbal medicine. However, three kinds of organophosphates pesticides are most frequently used in Goji berries by investigating the usage. Therefore, three pyrethroids pesticides (cypermethrin, fenvalerate, and deltamethrin) and three organophosphates pesticides (dichlorvos, omethoate, and malathion) were collected in the current study.
Also, according to Chinese Pharmacopoeia (2015) [9], five metals (arsenic (As), cadmium (Cd), lead (Pb), copper (Cu) and mercury (Hg)) need to be detected in in Chinese herbal medicine. However, Hg was not detected in previous reports [10–11], while nickel (Ni) and zinc (Zn), which would harmful to human health in high levels, were found in our pre-experiment [12]. Therefore, six metals (Pb, Cd, Cu, As, Ni and Zn) were selected in the present study.
Numerous studies have focused on the biological activities of Goji berries, however, only a few studies have investigated pesticides and metals present Goji berries, especially with a focus on their associated health risks. Concerning pesticides, Li et al. [7] identified 14 types of organophosphates pesticides in Goji berries using gas chromatography (GC). Huang et al. [13] also used GC to simultaneously detect 50 kinds of organochlorine and pyrethroid pesticides in Goji berries. Chen et al. [14] analyzed the etoxazole and pyridaben contents of Goji berries using GC method. Therefore, GC was also applied in the present study. These studies of pesticides in Goji berries did not discuss the associated health risks for consumers. While, recently, Fu et al. [15] detected 8 pesticides and evaluated the associated dietary risk. Jing et al. [16] analyzed 11 commonly used pesticide residues in Goji berries from Golmud area and conducted risk assessments for acute and chronic dietary exposures. Kim et al. [17] monitored pesticides in Goji berries and assessed the short-term and highest long-term risks. However, the health risks in these studies were determined only through deterministic assessment. Considering the uncertainty of metal concentrations and the variability of exposure parameters, deterministic assessment may overestimate or underestimate risks [18]. Probabilistic assessment can solve this problem by providing probabilities and identifying priority chemicals for risk control. Therefore, both deterministic and probabilistic assessments were performed in the present work.
Several studies have reported the presence of metals in Goji berries. Sa et al. [10] measured contents of macro- and microelements, such as Ni and Zn in Goji berries using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Kulaitienė et al. [19] also used ICP-OES method to detect metals in Goji berries. Wojcieszek et al. [8] used inductively coupled plasma mass spectrometry (ICP-MS) to quantify different metals in Goji berries. Rangsipanuratn et al. [20] also used ICP-MS to detect heavy metals in Chinese medicinal herbs, including Goji berries. Fu et al. [21] measured elements in some medicine food homologous (MFH) plants, including Goji berries, by ICP-tandem mass spectrometry (MS/MS). Xu et al. [22] used different methods to detect five toxic metals in Goji berries. The lead (Pb) and cadmium (Cd) contents were detected by graphite furnace atomic absorption spectrometry (GFAAS), the copper (Cu) content was determined through FAAS, and the mercury (Hg) and arsenic (As) contents were determined by atomic fluorescence spectrometry (AFS). ICP-OES combines a wide linear range, low detection limits, good sensitivity, widespread instrument availability, and reasonable cost [10]. Therefore, in this study, ICP-OES was used to identify and quantify the metals in Goji berries. In addition, most studies have focused on optimization methods or metal levels in different parts of Goji berries and the health risk of exposure through Goji berry consumption have been neglected. Therefore, an evaluation of the health risks posed by common metals in Goji berry is essential.
In summary, considering the simultaneous exposure to the main pollutants (pesticides and metals) in Goji berries and the uncertainty of risk assessment, this study was aimed to (1) analyze the concentrations of six pesticide residues (dichlorvos, omethoate, cypermethrin, fenvalerate, malathion, and deltamethrin) and six metals (Pb, Cd, Cu, As, Ni and Zn) in Goji berries obtained from different sources in Ningxia, China; (2) determine the daily exposure to these hazardous chemicals from Goji berries; and (3) assess the health risks for consumers using deterministic and probabilistic methods.