This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Let me give you an example: Passage: The French and Indian War (1754–1763) was the North American theater of the worldwide Seven Years' War. The war was fought between the colonies of British America and New France, with both sides supported by military units from their parent countries of Great Britain and France, as well as Native American allies. At the start of the war, the French North American colonies had a population of roughly 60,000 European settlers, compared with 2 million in the British North American colonies. The outnumbered French particularly depended on the Indians. Long in conflict, the metropole nations declared war on each other in 1756, escalating the war from a regional affair into an intercontinental conflict.
The answer to this example can be: When was the French and Indian War?
Here is why: This question is based on the following sentence in the passage- The French and Indian War (1754–1763) was the North American theater of the worldwide Seven Years' War. It is a common convention to write (start year-end year) beside a historical event to understand when the event happened. You can ask questions like this one about dates, years, other numerals, persons, locations, noun phrases, verb phrases, adjectives, clauses etc. which exist in the paragraph.

OK. solve this:
Small-scale artisanal mining of gold is another source of dangerous child labour in poor rural areas in certain parts of the world. This form of mining uses labour-intensive and low-tech methods. It is informal sector of the economy. Human Rights Watch group estimates that about 12 percent of global gold production comes from artisanal mines. In west Africa, in countries such as Mali - the third largest exporter of gold in Africa - between 20,000 and 40,000 children work in artisanal mining. Locally known as orpaillage, children as young as 6 years old work with their families. These children and families suffer chronic exposure to toxic chemicals including mercury, and do hazardous work such as digging shafts and working underground, pulling up, carrying and crushing the ore. The poor work practices harm the long term health of children, as well as release hundreds of tons of mercury every year into local rivers, ground water and lakes. Gold is important to the economy of Mali and Ghana. For Mali, it is the second largest earner of its export revenue. For many poor families with children, it is the primary and sometimes the only source of income.
Answer:
What is another source of mining dangerous to children workers?