They don't, they bind to the melatonin receptor. Which melatonin also binds to. This receptor is involved in a number of downstream pathways some of which regulate our sleep-wake cycle.
Yes both Carbaryl and Carbofuran can diffuse through the skin.
Would washing fruits and vegetables remove them yes, though if recently applied they may be present in the fruit/vegetable (more an issue for home gardeners, store bought would be long past the metabolic breakdown time and they would be long gone).
Ok, thanks for the clarification! So when the author talks about melatonin interference, what he really means is carbaryl and carbofuran interfering with its receptors.
That being said, if melatonin couldn't bind with its receptor, wouldn't that increase melatonin's concentration in the body? For example, the author writes "there is growing evidence that melatonin has important roles to play in cardiovascular disease - heart attacks, angina, heart failure etc" and "decreased levels of melatonin have been associated with higher levels of many types of cancer". Wouldn't that help combat these things? Or is this related more to sleep?
The role it plays in those chronic illnesses are seemingly due to melatonin's role in maintaining the sleep-wake cycle. Disruption of that bodily circadaen rhythem is thought to increase the likelihood of cancer, diabetes, heart disease etc.
It's not about the intracellular concentration of melatonin, it's variable and is cycled every day. It's more about activation of the melatonin receptors at the wrong time and disruption of the circadaen rhythem. At least that was how I understood the paper.