This is clearly a big topic with lots of aspects to it. There are plenty of examples of suffering in the novel, and you might want to think about how suffering is experienced by the following pairs of characters: Ammu and Velutha, Rahel and Estha, Chacko and Margaret. Of course, when we think about exploitation, you need to consider how Estha and Rahel are exploited terribly - both in the abuse of Estha at the cinema and in the way that they are forced to turn against Velutha and are used by adults. This of course is intimately linked to their suffering and sense of guilt later on in their lives.