Reports by the Congressional Research Service from 2008 discuss emerging policy issues regarding carbon dioxide pipelines for carbon sequestration, network needs and cost uncertainties regarding pipelines for carbon dioxide control, and jurisdictional issues in regulating carbon dioxide sequestration pipelines.
Total numbers of speakers is high: over 40 million Farsi speakers (about 60% of Iran's population); over 14 million Dari Persian speakers in Afghanistan (50% of the population according to CIA World FactBook & Britannica); and about 2 million Dari Persian speakers in Pakistan.
In fact, Arabic (in all its varieties) has 202 million speakers world-wide, and with this count would be #4 on the list above. However, Ethnologue considers the local colloquial varieties of Arabic to be separate languages, and the largest single colloquial is Egyptian, with 42.5 million speakers.