Explanation:

- The Census of India primarily focuses on collecting data about the *population*.

- It records numbers, distribution, growth rate, and various demographic details about the people in India.

- This extensive data collection happens every ten years and is crucial for understanding population dynamics.

- Industrial production data is generally compiled through economic and manufacturing surveys rather than the census.

- Pollution levels are typically monitored by environmental agencies and reported in separate studies, not the census.

- Food security is often assessed through agricultural production data and separate socio-economic surveys.