Introduction

Fish is a nutritious and valuable food, rich in easily digestible, high-quality protein, vitamins, minerals, and polyunsaturated fatty acids (PUFAs), particularly omega-3 fatty acids, which support cardiovascular and brain health, immunity, and overall growth1. In Egypt, fish is widely consumed across all socioeconomic groups as a healthy, flavorful, and affordable source of animal protein. Egypt’s per capita fish consumption was approximately 20.84 kg in 2022, ranking fifth in Africa2.

Egypt is considered a leading fish-producing country owing to its distinctive geographical location at the northeastern corner of Africa, with a coastline of around 2500 km on both the Mediterranean Sea and Red Sea, in addition to several lakes (Manzala, Bardawil, Burullus, Mariout, and others), and the Nile River with its tributaries3,4. Although Egypt ranks among Africa’s top fish producers, imports are still required to satisfy demand. Recent economic pressures, such as rising inflation and currency shortages, have pushed fish prices higher, causing a slight reduction in per capita consumption5.

In Egypt, marine and coastal fisheries play an important role in the local seafood supply, particularly in coastal cities such as Alexandria, Port Said, and Damietta3. Among the commonly consumed marine fish species in Egypt are flathead grey mullet (Mugil cephalus), locally known as Bouri, sardine (Sardinella aurita), and mackerel (Scomber scombrus) because of their affordability and nutritional value, as they are rich in high-quality protein, minerals, and omega-3 PUFAs6–8. Nevertheless, marine fish can accumulate heavy metals from contaminated aquatic environments, potentially increasing human exposure through fish consumption. The extent of heavy metal accumulation may vary among fish species depending on factors such as fish size, diet, water quality, habitat, and other ecological characteristics7.

The flathead grey mullet is a cosmopolitan, omnivorous species with coastal-pelagic habits, predominantly inhabiting estuaries, lagoons, and shallow coastal waters at depths of less than 20 meters7,9. Sardine is a small pelagic fish, distributed mainly in tropical and subtropical seas, including the Mediterranean Sea7. Sardine is a plankton-feeding fish that has a vital role in the marine food web through transferring energy and nutrients from planktonic organisms to higher predators10. Mackerel is also a commonly consumed pelagic fish in Egypt, reaching the Egyptian market through frozen imports and fresh catches from fisheries along the Mediterranean and Red Sea coasts6.

Heavy metals (HMs) are persistent metallic elements of high atomic weight and density that can enter aquatic environments through both natural processes, such as dissolution from the Earth’s crust, and anthropogenic activities, including agriculture, industrial processes, urbanization, sewage disposal, and surface runoff11–14. HMs include both toxic elements such as mercury (Hg), arsenic (As), lead (Pb), and cadmium (Cd), as well as essential metals such as copper, zinc, and iron, which are indispensable for human health but can be toxic above their threshold levels15. The Agency for Toxic Substances and Disease Registry (ATSDR) listed Hg, As, Pb, and Cd among the top ten most hazardous substances, highlighting their potential health hazards16. The bioaccumulation of HMs in fish tissues may be affected by various factors, including the fish’s size, age, sex, living environment, feeding behavior, and swimming patterns17. Additionally, seasonal variations and water quality can influence metal accumulation and associated health risks in aquatic organisms18. Furthermore, sediment characteristics can act as important drivers of heavy metal bioaccumulation in fish and associated human health risks19,20.

From a public health perspective, consuming contaminated marine fish with HMs beyond recommended levels could increase the risk of neurological damage, renal disease, liver disease, and other serious conditions21. Mercury, particularly methylmercury, is highly toxic to the nervous system, while arsenic is ranked first among the top ten most hazardous substances by ATSDR16. Arsenic is a highly toxic element; however, more than 90% of As in marine fish occurs in organic forms, which are less toxic, whereas only 0.02–11% is inorganic As, which is highly toxic22. Inorganic As could cause cardiovascular dysfunction, skin disorders, neurological injury, liver damage, and malignancy on long-term exposure23. Lead exposure may impair hemoglobin synthesis and cause neurological, renal, and reproductive disorders, whereas cadmium (Cd) is classified as a Group 1 human carcinogen by the International Agency for Research on Cancer (IARC). Moreover, the ingestion of foods contaminated with cadmium can disrupt vital physiological functions and cause nephrotoxicity, hepatotoxicity, and cardiovascular disorders23,24.

Exposure to Hg, As, Pb, and Cd has become a growing public health concern; therefore, several international and national organizations have established maximum permissible limits (MPLs) for these contaminants. Previous studies in Egypt have evaluated the health risks of consuming HMs by estimating the Estimated Daily Intakes (EDIs) and comparing them with safety thresholds, such as the Provisional Tolerable Daily Intake (PTDI) and Benchmark Dose Level (BMDL) established by regulatory organizations, such as the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and the European Food Safety Authority (EFSA)3,6–8,25. Health risk assessment generally considers both non-carcinogenic and carcinogenic effects. Non-carcinogenic risk refers to the potential for adverse health effects other than cancer and is commonly evaluated using the target hazard quotient (THQ) and total target hazard quotient (TTHQ), whereas carcinogenic risk represents the estimated lifetime probability of developing cancer and is assessed using the cancer risk (CR) index26,27.

Mansoura is a major Egyptian city, where marine fish, including flathead grey mullet, sardine, and mackerel, are widely marketed and consumed. Compared with previous Egyptian studies, the present study focuses on commercially available marine fish collected from retail markets in Mansoura and considers both general and high-fish consumption scenarios. Therefore, this study aimed to determine the concentrations of mercury (Hg), arsenic (As), lead (Pb), and cadmium (Cd) in flathead grey mullet, sardine, and mackerel marketed in Mansoura, Egypt, using atomic absorption spectrophotometry (AAS), with the analytical method validated for linearity, precision, recovery, and detection and quantification limits, and to assess potential health risks using the estimated daily intake (EDI), target hazard quotient (THQ), total target hazard quotient (TTHQ), and cancer risk (CR(.