Answer:
This study  casts doubts as the hypothesis does not support the women who are smokers, drinkers or use dyes besides the difference of breasts implants.
Step-by-step explanation:
This study  casts doubts as the hypothesis does not support the women who are smokers, drinkers or use dyes.
If the null and alternate hypothesis are formulated as 
H0 : silicone breasts implants cause illness in smokers, drinkers and hair dyed people 
against the claim
Ha: silicone breasts implants do not cause illness in smokers, drinkers and hair dyed people 
then there would be no doubt .
But as the null and alternate hypothesis are 
H0: silicone breast implants cause illness in women
against the claim 
Ha: silicone breast implants do not cause illness in women
This suggests that both categories of women have same characteristics. 
But actually both categories do not have same characteristics. The breast implant women also , smoke, drin and dye hair.
So when the characteristics are changed the illness maybe caused by some other characteristics.