Even though his main interest was biostatistics, Pearl had a wide range of interests in biology and was known for his broad knowledge of the subject. He published works on animal behavior, population growth, food and prices, Jewish and Christian marriages, and vegetarianism. In the 1920s and 1930s, Pearl focused on the effect that the environment, which included disease, alcohol, and tobacco, has on longevity. He published a book called "Alcohol and Longevity" in 1926, where he claimed that moderate consumption of alcohol could be beneficial for cardiovascular health, which was met with much debate due to prohibition. Controversy continued when Pearl conducted a study on tobacco in which he demonstrated that smoking decreases longevity while drinking does not.