Los investigadores analizaron la relación entre el riesgo de cáncer de pulmón y el contenido de alquitrán de la marca de cigarrillos que fumaban en 1982 un total de 364.239 varones y 576.535 mujeres que entonces tenían más de 30 años.
Fumar cigarrillos muy bajos en alquitrán (menos de 7 mg) o bajos (de 8 a 14 mg) comporta el mismo riesgo de cáncer pulmonar que fumar cigarrillos con contenido de alquitrán normal (15 a 21 mg). Lo que sí se ha observado que las personas que fuman cigarrillos sin filtro que contienen más de 22 mg de alquitrán presentan un riesgo mayor de desarrollar el citado tipo de tumor.
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