Thiruvananthapuram, Oct. 13: People living by the seaside in the Chavara-Neendakara area of Kerala, who are exposed to 10 times more radiation than the worldwide average, show a high rate of hereditable “point mutation” — a change in one of the four bases that make up the genetic code, according to a study.
The results of the study by scientists of the National Academy of Sciences, USA, might prompt a reconsideration of the legal safety limits for radiology workers, who are allowed to receive up to 50 times the normal level of radiation on the assumption that it is a “reasonably safe limit”.
The monazite sands in this seaside region of Kollam, which contain the radioactive element thorium, have been the subjects of much research. The latest study — in a densely-populated strip along the national highway where many fisherfolk live — has looked at the DNA from mitochondria, the tiny energy factories that power the cells.
The study, conducted on 988 people of the area, found that those living in the high background radiation belt had higher levels of point mutation in their mitochondrial DNA, which are inherited maternally and are simple to trace within lineages. In the high-radiation zone, the study found 22 mutations in which the mitochondria contained both mutant and original DNA. However, only one mutation was found in the low-radiation area.
The study also found that the point mutations caused by radiation in the mitochondrial DNA tended to occur in places prone to natural evolutionary change. Radiation appeared to accelerate this natural pace 12-fold. As such, the results of the study will also be of interest to evolutionary geneticists, who rely on a constant mutation rate of dating history.
“Whether such point mutations also affect genes that are implicated, for example, in cancer, needs to be explored in further genetic studies,” said Peter Forster of the University of Cambridge, one of the authors of the study.