Carcinogenicity and Toxicity of Hydrocarbons - UNSOLVED PRACTICE SET

Q7. What are polycyclic aromatic hydrocarbons (PAHs)? Name two common sources of PAH exposure in daily life.

Q8. Explain why benzene is more toxic than toluene, even though both are aromatic hydrocarbons.

Q9. How does benzo[a]pyrene, present in cigarette smoke and burnt food, cause cancer at the molecular level?

Q10. Why is prolonged exposure to LPG (liquefied petroleum gas) in poorly ventilated kitchens harmful? What precautions should be taken?

Q11. Your family uses a chulha (traditional stove) for cooking in the village. Explain why indoor air pollution from biomass burning is a serious health concern in rural India.

Q12. Why are unleaded petrol and catalytic converters recommended for vehicles? How do they reduce the emission of toxic hydrocarbons?

Q13. Discuss the carcinogenicity and toxicity of benzene and polycyclic aromatic hydrocarbons (PAHs):

(a) Sources of benzene exposure (petrol, industrial solvents, cigarette smoke)

(b) Mechanism of benzene toxicity — metabolism to benzoquinone and hydroquinone, DNA damage

(c) Sources of PAHs (incomplete combustion, grilled food, vehicle exhaust)

(d) Mechanism of PAH carcinogenicity — formation of diol epoxides, binding to DNA

(e) Health effects: leukaemia, lung cancer, skin cancer

Q14. Explain the toxicity of various hydrocarbons and their environmental impact:

(a) Carbon monoxide (CO) — mechanism of toxicity, symptoms of poisoning, treatment

(b) Methane and LPG — asphyxiation risk, explosion hazard

(c) Volatile organic compounds (VOCs) — indoor air pollution, sick building syndrome

(d) Petroleum hydrocarbons in soil and water — contamination of groundwater in India

Discuss preventive measures for each.

Q15. Hydrocarbon toxicity is a major public health concern in India. Discuss:

(a) Why Delhi's winter air pollution (smog) contains high levels of PAHs and benzene derivatives from vehicle exhaust and crop burning

(b) The health impact of using kerosene lamps and biomass chulhas in rural Indian households

(c) Government initiatives to reduce hydrocarbon toxicity: Bharat Stage VI norms, Pradhan Mantri Ujjwala Yojana (LPG connections)

(d) Individual actions students and families can take to reduce exposure to toxic hydrocarbons

Q16. The concentration of benzene in a factory workplace is measured at 5 ppm (parts per million) by volume.

(a) Convert this concentration to mg/m³ at 25°C and 1 atm pressure. (Molar volume at 25°C = 24.5 L)

(b) The permissible exposure limit (PEL) for benzene is 1 ppm (8-hour TWA). Calculate by what factor the measured concentration exceeds the PEL.

(c) If a worker is exposed for 8 hours daily at this level, calculate the total volume of benzene inhaled. (Assume breathing rate = 10 L/min)

Q17. A study found that 100 g of charred grilled chicken contains 0.5 μg of benzo[a]pyrene (BaP).

(a) The tolerable daily intake of BaP is recommended at 0.004 μg per kg body weight. For a 60 kg adult, calculate the maximum safe daily intake.

(b) How many grams of charred grilled chicken can this adult safely consume per day?

(c) If the cancer risk from BaP is estimated at 1 in 100,000 per μg consumed daily over a lifetime, calculate the additional cancer risk for someone eating 200 g of this chicken daily.

Q18. Delhi's air quality index (AQI) frequently crosses 400 (severe category) in November due to stubble burning and vehicular emissions. The PM2.5 concentration reaches 300 μg/m³, of which 10% is estimated to be PAHs.

(a) Calculate the PAH concentration in μg/m³.

(b) If a person breathes 15 m³ of air per day, calculate the daily PAH intake.

(c) The WHO guideline for annual average PM2.5 is 5 μg/m³. Calculate by what factor Delhi's November PM2.5 exceeds this guideline.

(d) Suggest three practical measures that Delhi residents can take to reduce their exposure during severe pollution episodes.