Lead contamination is highest in Sydney's inner west with indoor levels worse than outdoor levels, a new study has found.

Macquarie University environmental science professor Mark Taylor, who led the research, said it was the "biggest study of its kind in Australia on indoor dust".

Homes trap more contaminants than outdoor areas, the new study says. Credit:Dragon Images

The study examined indoor dust from vacuum cleaners in 224 homes in suburbs across Sydney looking for concentrations of harmful elements such as lead.

The government-funded study gave Professor Taylor and his team of scientists a unique opportunity to peer inside people's homes to examine levels of contaminants.