The present levels of particles in the air present a serious health problem in Sweden and legal quality standards for particles are violated. The article analyses if the environmental quality standard is possible to maintain by present legislation, if the standard is based on scientific facts concerning which types of particles that are most hazardous, and if the proposed legally based action programme for counteracting particle concentrations in Stockholm beyond the limits is effective. It suggests developed legislation, a new standard for fine particles and increased focus on traffic reducing measures, if the standards are to be maintained