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Safety accidents can occur during the production, storage, transportation, use, and handling of hazardous chemicals, as well as in their waste disposal processes; these accidents pose a serious threat to human safety and health and can cause environmental pollution, which has thus drawn widespread attention. To this end, our country has issued a series of regulatory documents such as the “Regulations on the Safety Management of Hazardous Chemicals”. It is very important to understand the hazards of hazardous chemicals, enforce laws and regulations on safe production, and ensure safe and civilized production practices. 1 Overview of Hazardous Chemicals 1.1 Definition Substances such as elements, compounds, and their mixtures, whether natural or man-made, are collectively referred to as chemicals. Chemicals that possess properties such as explosiveness, flammability, toxicity, corrosivity, or radioactivity, and that can cause harm to humans, facilities, or the environment, are considered hazardous chemicals. 1.2 Classification of hazardous chemicals: In accordance with the **standard “Classification and Labelling of Dangerous Goods” (GB6944), hazardous chemicals are divided into 9 categories, with some of these categories further subdivided into subcategories. These categories and subcategories are listed as follows: Category 1: Explosives; Subcategory 1.1: Substances and articles with a risk of overall explosion; Subcategory 1.2: Substances and articles with a risk of projection but no risk of overall explosion; Subcategory 1.3: Substances and articles with a risk of combustion and either a risk of local explosion or a risk of local projection, or both, but no risk of overall explosion; Subcategory 1.4: Substances and articles that present no significant risk; Subcategory 1.5: Very insensitive substances with a risk of overall explosion; Subcategory 1.6: Extremely insensitive substances with no risk of overall explosion. Category 2: Gases; Subcategory 2.1: Flammable gases; Subcategory 2.2: Non-flammable, non-toxic gases; Subcategory 2.3: Toxic gases. Category 3: Flammable liquids. Category 4: Flammable solids, substances that are readily self-igniting, and substances that release flammable gases when in contact with water; Subcategory 4.1: Flammable solids; Subcategory 4.2: Substances that are readily self-igniting; Subcategory 4.3: Substances that release flammable gases when in contact with water. Class 5: Oxidizing substances and organic peroxides; Subclass 5.1: Oxidizing substances; Subclass 5.2: Organic peroxides. Category 6: Toxic and infectious substances; Subcategory 6.1: Toxic substances; Subcategory 6.2: Infectious substances. Category 7: Radioactive materials. Category 8: Corrosive substances. Category 9: Miscellaneous dangerous substances and articles. There are 3,828 hazardous chemicals listed in the Catalog of Hazardous Chemicals (2002 edition) (excluding radioactive substances). 1.3 Highly toxic chemicals: Highly toxic chemicals refer to those that pose extreme toxicity hazards, including synthetically produced chemicals and their mixtures (including pesticides) as well as natural toxins. Thresholds for determining the toxicity of highly toxic chemicals: In rat tests, the oral LD50 should be ≤50 mg/kg, the dermal LD50 should be ≤200 mg/kg, and the inhalation LC50 should be ≤500 ppm for gases, or 2.0 mg/L for vapors, or 0.5 mg/L for dusts and mists. For data on dermal LD50, values from rabbit tests can be used as a reference. The “Catalog of Highly Toxic Chemicals” (2002 edition), jointly issued by eight central ministries and bureaus in our country, lists 335 highly toxic chemicals. 2 Hazards of Hazardous Chemicals 2.1 Multiplicity and Complexity of Hazards Since substances are complex and variable in nature, their hazards are determined by various factors; as a result, the hazards associated with a particular hazardous chemical can be diverse. If it is flammable, explosive, or oxidizing, it may also possess toxicity, radioactivity, and corrosivity. A substance does not have just one type of hazard – for example, zinc phosphide releases flammable gases when it comes into contact with water, and it is also highly toxic; nitric acid is highly corrosive as well as highly oxidizing. 2.2 Hazards of explosives 2.2.1 Explosiveness Explosives can undergo violent explosions when exposed to external energy sources such as heat, impact, friction, or electric sparks, resulting in casualties, the collapse of buildings, damage to equipment, and severe losses. 2.2.2 Spontaneous ignition risk: Some explosives can catch fire or explode on their own at certain temperatures, without the need for an external heat source. If dual-base materials are stored together for an extended period of time, the heat generated by their slow thermal decomposition, along with the NO2 gases produced, cannot dissipate in time; when this accumulated heat reaches the ignition point, the materials will catch fire or explode on their own. Special attention must be paid to safety issues during the storage and transportation of such items. 2.2.3 Static electricity hazards: **It is a poor conductor of electricity. During production, packaging, transportation, and use, it often comes into friction with containers or other materials, resulting in the generation of static charges. If no effective measures are taken to discharge these static charges, they will accumulate. When the accumulated charge reaches a certain voltage level, a discharge spark occurs, which can lead to fires and explosions. 2.2.4 Toxicity Some substances, such as picric acid, TNT, nitroglycerin, mercuric fulminate, and lead azide, possess inherent toxicity; exposure to them by humans can lead to toxic effects. 2.3 Flammability Hazard Many hazardous chemicals are flammable, such as flammable gases, flammable liquids, flammable solids, and some toxic substances; they pose a flammability risk and can cause fires when the surrounding environment meets the conditions for combustion. 2.4 Hazard of toxicity Toxic substances possess severe toxicity; exposure to them in the human body can lead to poisoning incidents, while leaks can cause environmental pollution. 2.5 Radioactive hazards: Radioactive materials possess high radiation levels; when the human body is exposed to them, it can lead to external or internal exposure, with ionizing radiation causing acute or chronic radiological diseases. If a leak occurs, a radioactive contamination accident takes place. 2.6 Corrosive hazard: Corrosive substances, whether acidic, alkaline, or of another type, possess severe corrosive properties; contact with them can cause chemical burns in the human body, and some of them can also lead to poisoning. Substances such as formaldehyde are also carcinogenic. 3 Occupational hazards of hazardous chemicals 3.1 Dust-induced pneumoconiosis When certain solid hazardous chemicals turn into dust and are dispersed in the ambient air, prolonged exposure to such dust by workers can lead to pneumoconiosis; for example, aluminum dust can cause aluminum pneumoconiosis. 3.2 Occupational poisoning: The vast majority of hazardous chemicals, not only toxic substances but also many explosives, flammable gases, flammable liquids, flammable solids, oxides, and organic oxides, can cause occupational poisoning in workers. Occupational poisoning can be divided into acute poisoning and chronic poisoning. The symptoms of poisoning vary: in some cases it causes symptoms related to neurasthenia syndrome; in other cases it leads to irritation of the respiratory system, manifesting as tracheitis, pneumonia, or pulmonary edema. It can also cause toxic liver disease or toxic kidney disease. In some instances it damages the blood system, resulting in hemolytic anemia, leukopenia, and changes in hemoglobin such as methemoglobin, carboxyhemoglobin, and sulfhemoglobin, which leads to tissue hypoxia and suffocation. It may also cause damage to the digestive system, urinary system, reproductive system, and others. 3.3 Radiation-induced diseases: Radioactive substances can cause various radiation-induced diseases. In the List of Occupational Diseases, there is 1 type of radiological disease included in the list of occupational diseases, all of which are caused by radioactive rays. 3.4 Occupational dermatitis Occupational dermatitis includes 8 types of skin diseases such as contact dermatitis and photosensitive dermatitis; among these, except for electrodermatitis, the other 7 types of occupational dermatitis can be caused by hazardous chemicals. Therefore, the harm that hazardous chemicals can cause to the skin must be given due attention. 3.5 Occupational Tumors Eight types of occupational tumors are listed in China’s “Catalogue of Occupational Diseases” as statutory occupational diseases. Each of these occupational tumors is caused by hazardous chemicals. It has now been confirmed through experiments, or suggested by data from occupational epidemiological studies, that many other hazardous chemicals are carcinogenic, such as formaldehyde. 3.6 Occupational diseases caused by biological factors There are 3 types of occupational diseases caused by biological factors that are listed as such under China’s statutory regulations: anthrax, forest encephalitis, and brucellosis, all of which are caused by infectious substances classified in Category 6 of hazardous chemicals. 3.7 Occupational eye diseases Among the legally recognized occupational diseases in our country, conditions such as “chemical eye burns” and “occupational cataracts” are caused by hazardous chemicals. 3.8 Occupational diseases of the ear, nose, throat, and mouth: Among the legally recognized occupational diseases of the ear, nose, throat, and mouth in our country are “chromic nasal disease” and “tooth erosion,” which are caused by hazardous chemicals. 3.9 Other occupational diseases Among the other occupational diseases recognized by law in our country, conditions such as \"metal fume fever,\" \"occupational asthma,\" and \"occupational hypersensitivity pneumonitis\" are caused by hazardous chemicals. 4 Measures for Preventing and Controlling the Hazards of Hazardous Chemicals: It is difficult for a single measure to be effective in addressing the hazards posed by hazardous chemicals; a series of comprehensive measures must be taken simultaneously in order to eliminate these hazards. 4.1 Organizational and management measures 4.1.1 Thoroughly implement laws and regulations on work safety. Hazardous chemicals-related enterprises must strictly abide by a series of laws and regulations in China, including the Work Safety Law, the Law on the Prevention and Control of Occupational Diseases, the Regulations on the Safety Management of Hazardous Chemicals, and the Regulations on Labor Protection in Workplaces Using Toxic Substances. 4.1.2 Establishment of safety and health management organizations: Hazardous chemical handling enterprises should establish safety and health management organizations or designate a department responsible for the safe management of hazardous chemicals, to ensure that there is no gap in such management. 4.1.3 Appointment of safety and health management personnel: Hazardous chemical handling enterprises should have safety and health management personnel in their management structure to oversee the safety and health of those who work with hazardous chemicals. 4.1.4 Establishment of safety and health management regulations: Hazardous chemical handling enterprises must establish safety and health management regulations to standardize the safety behaviors and health habits of their employees. 4.2 Engineering and technical measures 4.2.1 Adhere to the \"three simultaneities\" principle: When hazardous chemical enterprises carry out projects involving new construction, renovation, expansion, or the introduction of new technologies, their safety and health facilities must be designed, constructed, and put into use simultaneously with the main structure of the project. Pre-evaluations of safety and occupational health must be conducted for engineering design; post-completion inspections of safety and occupational health are required after the project is finished. 4.2.2 Adopt new technologies and processes to eliminate occupational hazards. The production processes for hazardous chemicals should make use of new technologies and processes as much as possible, employ microcomputer control and isolated operations, in order to prevent workers from having direct contact with hazardous chemicals. 4.2.3 Improve ventilation and enhance the working environment. Production facilities should preferably be of frame-type design to facilitate the dispersion of any leaks that may occur; production plants need to have adequate general ventilation as well as local exhaust systems to ensure that the air in the area where workers are located remains fresh at all times. 4.2.4 Conduct regular safety inspections to prevent accidents. All facilities used for the production of hazardous chemicals must undergo regular maintenance and inspections. During maintenance, the equipment has to be disassembled, and leaks can easily lead to accidents. Therefore, it is essential to develop a maintenance plan before carrying out repairs, obtain all necessary safety permits, take appropriate protective measures, and have someone supervise the process to prevent accidents. 4.3 Health and safety measures 4.3.1 Occupational health monitoring Hazardous chemical handling enterprises must conduct health checks on their employees before they start working, during their employment, before they leave the job, and in emergency situations, and must maintain records of such occupational health monitoring. Workers with occupational contraindications must not be assigned to tasks for which they have such contraindications. 4.3.2 Regular monitoring of the working environment: The concentration of hazardous chemicals in the air of the workplace where such chemicals are used must be monitored on a regular basis. The results of these measurements should be made public, and occupational health records should be established; these measurement results must also be archived. 4.3.3 Health foods such as milk should be provided to workers engaged in toxic and harmful tasks, in order to enhance their physical condition and resistance to diseases. 4.4 Implement proper personal protection 4.4.1 Enterprises that supply personal protective equipment must provide workers with qualified and effective personal protective equipment in accordance with **relevant regulations. Such as work uniforms, respiratory protection, protective gloves, etc., and teach workers how to use them correctly. 4.4.2 Personnel must not start working without wearing protective equipment; they are not allowed to engage in operations without proper personal protective gear. Managers should conduct strict inspections and enforce the rules rigorously. 4.4.3 Inspect and maintain protective equipment; companies should strengthen the management of such equipment, store it in designated locations, conduct regular inspections, and carry out timely repairs to ensure it remains in good condition at all times.