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Frequencies of spontaneous abortion were studied in populations located at different distances from the Rönnskår smelter in northern Sweden. The smelter emits a number of potentially genotoxic substances like lead, arsenic and sulphur dioxide to the environment. In the population located close to the smelter a significant increase of the abortion frequency was found, compared to more distantly located populations.

A retrospective study on reproductive hazards was performed among 542 employees at Swedish power plants. Questionnaires were answered by 89% of the employees. Data on pregnancies were checked by studying hospital case records. There was a statistically significant, decreased frequency of "normal" pregnancy outcome, almost exclusively due to an increased frequency of congenital malformations, when the father was a high-voltage switchyard worker. The differences in pregnancy outcome could not be explained by any of the confounding factors analyzed. The total number of children with malformations (26) and the total number of pregnancies in this study, however, were very small.

In vivo and in vitro studies of the clastogenic effects of power frequency electric fields and transient electric currents have been performed. For the in vivo investigation peripheral lymphocytes from twenty switchyard workers were screened for chromosome anomalies. The rates of chromatid and chromosome breaks were found to be significantly increased compared to the rates in 17 controls. Exposure of human peripheral lymphocytes, in vitro, to a 50-Hz current with 1 mA/cm2 current density did not induce any chromosome damage. Exposure to ten 3 mus-long spark discharge pulses with a peak field strength in the samples of 3.5 kV/cm, however, resulted in chromosome breaks at a frequency similar to that induced in lymphocytes in vitro by ionizing radiation at 0.75 Gy. The biological significance of chromosomal damage induced in somatic cells is discussed.

The Rönnskär smelter in northern Sweden emits a number of potentially toxic substances, of which arsenic, lead and sulphur dioxide have caused most public concern. Birth weight was studied in the offspring of women working at the Rönnskär smelter and in four populations (A–D) at different distances from the smelter. In the offspring of employees and in two small industrial populations (A and B) close to the smelter a significantly decreased birth weight was found. This decrease showed a consistent parity dependence, affecting mainly later pregnancies.

From a total of 21 probands, found mainly by a thorough study of case records at the department of Ophthalmology, the University Hospital, Umeå, a total of 95 cases of hereditary macular degeneration were traced by genealogical and clinical investigations in the county of Västerbotten, Sweden. 75 of the cases belong to the same family, with a total of 125 affected members, 65 men and 60 women. 23, however, were dead, and 27 had left the county when the survey was finished. The disease has been traced back to a settler who came from Dalecarlia, and he is probably related to a Dalecarlian family with hereditary macular degeneration described by Barkman in 1961. The family is presented in three pedigrees. The defect is inherited as an autosomal dominant trait with a very high but not complete penetrance and a very variable expressivity. Age of onset of the deterioration of sight varies from early childhood to more than 50 years. 20 of the 95 cases belong to some smaller, separate families with varying heredity, presented in nine pedigrees. Seven cases, representing all known patients with a condition resembling hereditary macular degeneration for which no heredity could be proved are also presented.

A significantly increased frequency of chromosomal aberrations was found among lead‐exposed workers at the Rönnskär smelter in northern Sweden. The frequency of aberrations showed a correlation with lead exposure as measured by the blood levels of lead. Strong individual variations were found. No synergistic effect of smoking was observed. Correlations were found between (chromosome and chromatid) breaks and gaps, which lends further support to the notion that gaps may be useful as indicators of genotoxic agents.

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