Which of the following substances are recognised as carcinogens, that is, cancer causing agents, in humans?

Introduction / Context:
Carcinogens are substances or environmental exposures that increase the risk of cancer in humans or animals. Understanding which chemicals and materials are carcinogenic is important for public health, workplace safety, and environmental protection. Many general knowledge questions test awareness of common carcinogens that people might encounter in industrial or polluted environments. This question asks you to identify which of the listed substances are recognised as carcinogens.

Given Data / Assumptions:

• The substances listed are cadmium, asbestos, and benzene.
• The question asks which are recognised as carcinogens, that is, agents that can cause or promote cancer.
• We assume awareness that international health agencies classify certain substances as carcinogenic based on scientific evidence.
• We focus on general classification, not on detailed exposure limits.

Concept / Approach:
Each of the three substances listed has been classified by major health organisations as carcinogenic to humans. Cadmium, a toxic heavy metal, is associated with lung cancer and other health issues in occupational settings. Asbestos, a fibrous mineral once widely used in construction and insulation, is strongly linked with lung cancer and mesothelioma. Benzene is an aromatic hydrocarbon found in some fuels and industrial solvents and is linked with blood cancers such as leukaemia. Since all three have established links to cancer, the most accurate answer is that all of the above are recognised carcinogens.

Step-by-Step Solution:
Step 1: Consider cadmium. It is a heavy metal used in batteries, pigments, and some industrial processes. Long term exposure, especially through inhalation in workplaces, has been linked to lung cancer and other serious health problems. Step 2: Consider asbestos. It was widely used for fireproofing and insulation but was later shown to cause lung cancer, mesothelioma, and other respiratory diseases when its fibres are inhaled. Step 3: Consider benzene. It is used as a solvent and is present in petrol and industrial emissions. Chronic exposure to benzene is associated with blood disorders and leukaemia. Step 4: Recognise that major health bodies list cadmium, asbestos, and benzene among proven or probable human carcinogens. Step 5: Therefore, the option stating that all of the above are recognised carcinogens is the correct choice.

Verification / Alternative check:
If you consult standard health and safety references or general science textbooks, you will find cadmium, asbestos, and benzene frequently listed in discussions of occupational and environmental carcinogens. Asbestos has been banned or strictly regulated in many countries due to its strong link with cancer. Benzene exposure limits are tightly controlled in workplaces because of its established link with leukaemia. Cadmium is also regulated due to its toxicity, including carcinogenic effects. This convergence of evidence for all three substances supports the conclusion that they are all carcinogenic.

Why Other Options Are Wrong:
Choosing only cadmium, only asbestos, or only benzene would ignore the well documented carcinogenic properties of the other substances. Each individual option describes a substance that is indeed a carcinogen, but the question asks which substances are recognised as carcinogens overall. Therefore, partial selections are incomplete and do not fully answer the question. The only option that reflects the true status of all three substances is the one stating that all of the above are carcinogens.

Common Pitfalls:
A common pitfall is to focus only on the most famous carcinogen among the list, such as asbestos, and forget that benzene and cadmium also carry cancer risks. Another mistake is to assume that only synthetic organic chemicals like benzene are carcinogenic, overlooking heavy metals and minerals. To avoid such errors, remember that carcinogens can include metals, minerals, and organic chemicals. When a question lists several well known hazardous substances, carefully consider whether more than one might be carcinogenic and check if an all of the above option is appropriate.

Final Answer:
The correct choice is All of the above are recognised carcinogens (cancer causing agents), because cadmium, asbestos, and benzene all have established links to cancer in humans.