This paper describes the background, aim and study design for the Swedish SELMA study that aimed to investigate the importance of early life exposure during pregnancy and infancy to environmental factors with a major focus on endocrine disrupting chemicals for multiple chronic diseases/disorders in offspring.
The cohort was established by recruiting women in the 10th week of pregnancy. Blood and urine from the pregnant women and the child and air and dust from home environment from pregnancy and infancy period have been collected. Questionnaires were used to collect information on life styles, socio-economic status, living conditions, diet and medical history.
Of the 8394 reported pregnant women, 6658 were invited to participate in the study. Among the invited women, 2582 (39%) agreed to participate. Of the 4076 (61%) non-participants, 2091 women were invited to a non-respondent questionnaire in order to examine possible selection bias. We found a self-selection bias in the established cohort when compared with the non-participant group, e.g. participating families did smoke less (14% vs. 19%), had more frequent asthma and allergy symptoms in the family (58% vs. 38%), as well as higher education among the mothers (51% vs. 36%) and more often lived in single-family houses (67% vs. 60%).
These findings indicate that the participating families do not fully represent the study population and thus, the exposure in this population. However, there is no obvious reason that this selection bias will have an impact on identification of environmental risk factors.
The aim was to elucidate the role of genetic variants on symptoms of the eyes and airways, headache and nausea, as well as on immunologic markers, among vulcanization workers in the contemporary Swedish rubber industry. Polymorphisms in genes, which are involved in the defense against reactive oxygen species and metabolism of toxic substances present in the vulcanization fumes, were analyzed.
One hundred and forty-five exposed and 117 unexposed workers were included in the study. Medical and occupational histories were obtained in structured interviews. Symptoms were recorded and immunologic markers analyzed in blood. Polymorphisms in glutathione-related genes (glutamate cysteine ligase catalytic subunit (GCLC)-129, glutamate cysteine ligase modifier subunit (GCLM)-588, glutathione S-transferase alpha 1 (GSTA1)-52, GSTM1*O, GSTP1-105, GSTP1-114, and GSTT1*O) were analyzed by Taqman-based allelic discrimination and ordinary PCR.
A protective effect of GSTA1-52 (G/A + A/A) genotype on symptoms and immunologic cells, in particular among exposed workers, was suggested. Exposed workers with GSTT1*O had increased risk of nosebleed compared to exposed workers with GSTT1*1. Exposed workers with GSTP1-105 (ile/val + val/val) had decreased levels of total immunoglobulin E (IgE) compared to exposed workers with GSTP1-105 ile/ile. GCLC-129 variant genotype demonstrated increased levels of immunologic cells among exposed workers, although statistical significance was not reached.
Our data indicate that hereditary factors influence the susceptibility to symptoms and the immunologic response of workers in the rubber industry.