His later interest in introducing Christianity into China, led to familiarity with Chinese slavery and opium addiction. Long opposed to the former, he also became an active opponent of the Opium trade, writing two books to promote the banning of opium smoking: “Truth about Opium Smoking” and “The Chinese Opium Smoker”. In 1888 Broomhall formed and became Secretary of the Christian Union for the Severance of the British Empire with the Opium Traffic and editor of its periodical, "National Righteousness".
Broomhall’s subsequent focus on introducing Christianity to China led him to understand Chinese slavery and opium addiction. Initially opposed to both, he later became an active opponent of the opium trade, writing two books to promote banning opium smoking: "Truth about Opium Smoking" and "The Chinese Opium Smoker". In 1888, Broomhall founded and served as Secretary for the Christian Union against British Empire's opium traffic and edited its periodical, "National Righteousness".