Evaluation of ionizing radiation as a risk factor for the incidence of breast cancer: long-term analysis after the cesium-137 accident in Goiânia, Brazil. An ecological study

ABSTRACT BACKGROUND: The largest radiological accident to occur in any urban area happened in Goiânia, Brazil, in 1987. OBJECTIVE: To evaluate the association between breast cancer incidence and ionizing radiation levels. DESIGN AND SETTING: Ecological study among residents of the city of Goiânia, Brazil. METHODS: The central region of Goiânia, with seven major sources of contamination from cesium-137, was defined as the study area. The addresses of women diagnosed with breast cancer were identified between 2001 and 2010. The data were geographically referenced and, using census data, the annual averages of crude incidence rates were estimated. The existence of clusters of new cases was ascertained by means of the Moran index. Correlations of radiometric measurements with the incidence were assessed using unconditional linear regression. RESULTS: A total of 4,105 new cases were identified, of which 2,233 were in the study area, and of these, 1,286 (57.59%) were georeferenced. The gross rates of total and referenced cases were 102.91 and 71.86/100,000 women, respectively. These were close to the average for Brazilian state capitals, which is 79.37/100,000 women. The cluster analysis showed slight correlations in three small sets of census tracts, but these were far from the sources of contamination. The scatter plot of points and the R2 value close to zero indicated that there was no association between the variables. CONCLUSION: This study reinforces the hypothesis that the ionizing radiation levels to which women living in Goiânia are now exposed to are not associated with the onset of new cases of breast cancer.

Excess mortality during heat waves, Tehran Iran: an ecological time-series study

In the past three decades, Tehran, capital of Iran, has experienced warmer summers so we need to determine heat-related mortality to establish appropriate public health activities during hot summers. The aim of this study was to detect heat waves during the last decades and then determine excess mortality in immediate and lagged times. An ecological study based on time-series model was conducted in Tehran for re-cent decade using generalized linear lagged model [GLLM] with Poisson regression in 2001-2011. Maximum daily temperature was heat exposure for death outcome on the same day [lag 0], 3 [lag 01] and also 7 [lag 02] day moving average. Relative risk with 95% confidence was reported to quantify for increasing of daily mortalities for 1[degree sign]C risen exposure. Air pollutants considered as confounders in final model. Total excess mortality during 17 heat waves was 1069 [8.9 deaths/Heat wave days]. All non-external cause of death increased significantly during heat waves [3%-9%] with [RR= 1.03, 95% CI: 1.01, 1.05 and RR=1.09, 95% CI: 1.07, 1.09] and after adjusting for ozone and PM10 raised. Cause-specific deaths [especially circulatory disease] and death among elderly increased during heat waves [especially in the hottest wave]. The largest positive lagged effect of hot temperature although seen during hottest waves for all mortalities. Three waves had the most harvest effect for all categories of mortalities. This study showed excess mortalities resulted from hot temperatures and exacerbated with air pollutants in Tehran in the context of climate change. Forward displacement mortality and lagged mortalities were seen, but our results were not conclusive about the displacement pattern of mortalities

Indoor radon.

The naturally radioactive but chemically inert gas, radon, is formed from the radioactive decay of radium which is part of the uranium series. Radon gas, which has a half life of 3.8 days, must escape from soil particles through air-filled pores in order to enter the atmosphere following the decay of radium. The concentration of radon in the atmosphere varies, depending on the place, time, height above the ground and meteorological conditions. It is thus an inescapable source of radiation exposure, both at home and at work. The potential hazards posed by exposure to radiation from indoor radon gas and its daughter products are of great concern worldwide. Noting of an excessive lung cancer risk among several groups of underground miners exposed to radon and its daughter products, studies on radon concentrations in the workplace and in dwellings have been conducted in many countries. The results have shown that the distribution of radon concentrations are approximately lognormal from which population weighted; the arithmetic mean of radon concentration of 40 Bq.m-3 has been adopted worldwide for dwellings and workplaces. The principal methods for reducing a high indoor radon concentration are: reducing the radon supply by reversing the pressure difference between the building and the soil; raising the resistance of the foundations to soil gas entry; removing the radon sources such as water or underlying soil; diluting the concentration by increasing the ventilation rate; and reducing the concentration of radon progeny by filtering and increasing the circulation of indoor air. Buildings which have a radon concentration higher than 200 Bq.m-3 should be investigated by the national authorities concerned; meanwhile, householders should be advised to take simple temporary precautions, such as increasing ventilation, until a permanent remedy can be effected.