Lead: Lead is toxic to all systems of the human body. The main lesions are in the nervous system, hematopoietic system and blood vessels. In terms of the nervous system, high-level neurological dysfunction may occur in the early stage, and organic encephalopathy and nerve palsy may occur in the late stage. For the hematopoietic system, lead mainly interferes with the synthesis of heme and causes anemia. Lead has a great impact on children's growth and development. The brains of young children are more sensitive to lead pollution, which seriously affects children's intellectual development and behavior. 

Arsenic: Arsenic mostly exists in the form of inorganic arsenic and alkyl arsenic in the environment due to chemical and microbial effects. The toxicity of different forms of arsenic varies greatly. Trivalent arsenic compounds are more toxic than pentavalent arsenic compounds, with arsenic hydrogen and arsenic trioxide (commonly known as arsenic) being the most toxic. Oral administration of 5-50 mg of arsenic trioxide can cause poisoning, and 60-100 mg can cause death. Long-term exposure to arsenic can cause cell poisoning and sometimes induce malignant tumors. In particular, inorganic arsenic is a carcinogen for skin cancer and lung cancer. Arsenic can also pass through the placenta and damage the fetus.
Cadmium: Cadmium entering the body can damage blood vessels, cause tissue ischemia, and cause multi-system damage; cadmium can also interfere with the metabolism of trace elements such as copper, cobalt, and zinc, hinder intestinal absorption of iron, and inhibit hemoglobin synthesis. The metabolic process of oxidative phosphorylation in alveolar macrophages causes lung, kidney, and liver damage. Cadmium is a non-essential and toxic element for the human body and may be carcinogenic, teratogenic and mutagenic. 

Salmonella: Medical research shows that food poisoning caused by Salmonella is most likely to occur from May to October, and food poisoning caused by Salmonella is closely related to factors such as the content of Salmonella in the food, its pathogenicity, and individual susceptibility. When people eat food containing Salmonella, the bacteria and the toxins produced by the bacteria may cause adverse reactions such as vomiting, diarrhea, fever and headache, which may be severe and even life-threatening, causing great harm to the human body. 
Escherichia coli: Although the vast majority of Escherichia coli cooperate well with humans, there are still a small number of special types of Escherichia coli that are quite virulent and will cause serious epidemics once infected. Most of them are endogenous infections, mainly urinary tract infections, such as urethritis, cystitis, and pyelonephritis. It can also cause peritonitis, cholecystitis, appendicitis, etc. In infants, the elderly and infirm, patients with chronic wasting diseases, and patients with extensive burns, Escherichia coli can invade the bloodstream and cause sepsis. Certain serotypes of E. coli can cause diarrhea in humans. Among them, enterotoxigenic Escherichia coli can cause diarrhea in infants and tourists, ranging from mild watery diarrhea to severe cholera-like symptoms.