This work must also include redoubling efforts to prevent the supply of the precursor chemicals that are the foundation of so many illicit drugs.

在这项工作中，我们还必须加倍努力，防止供应前体化学品，因为此类化学品是很多非法药物的基础。

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The treaty lists the agents and precursor chemicals that will be subject to control.

CENTERFORSECURITYPOLICY: Chemical Weapons: Say No to This Troubled Treaty

The new plan goes further, aiming also at the supply of the precursor chemicals used to refine the drug and at money laundering.

ECONOMIST: Bolivia goes to war against coca

In 2011, the US director of national intelligence concluded that Syria remained "dependent on foreign sources for key elements" of its chemical weapons programme, including precursor chemicals, which are generally dual-use chemicals that can be combined to produce blister or nerve agents.

BBC: Syria's chemical weapons stockpile