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.

Indoor radon in Thailand: a study with particular reference to its sources.

Measurements of radon gas were carried out on each floor of the four tall concrete buildings. The results show clearly that levels of radon concentration on the higher floors of the buildings were mostly comparable and occasionally were much higher than the ground-floor in contact with the earth. Hence, the findings indicate that the source of indoor radon is not only the surrounding soil but also other sources in the buildings, i.e. most likely radium-containing building materials.

A survey of indoor radon in phuket province.

A study of indoor radon was carried out on 271 different buildings in the districts (Amphurs Thalang, Muang and Kratoo) of Phuket Province in Southern Thailand, using an activated charcoal canister for gaseous collection and a gamma spectrometer for analysis of the samples. The survey revealed the presence of radon gas inside all the buildings investigated, varying in concentration from 4 to 82.50 Bequerels/cubic metre (14.09 + 11.48 Bq.m-3), i.e., well below the threshold limit of 148 Bq.m-3 established by the American Environmental Protection Agency. The results of measurement of radon concentrations in Amphur Kratoo (22.27 + 18.93 Bq.m-3), Amphur Thalang (14.45 + 10.11 Bq.m-3), and Amphur Muang (10.25 + 5.95 Bq.m-3) showed a marked statistically significant difference (p < 0.005). In considering the age of the buildings (less than 1 year, 1-5 years and over 5 years old), types of building materials (concrete, wood, zinc sheeting and glass) and the apprarent difference of ventilation, the differences in indoor radon concentrations were not statistically significant (P > 0.05). Indoor cigarette smoking did not affect indoor radon concentrations (p = 0.072).

Indoor radon and lung cancer.

Fifty-four hourses, mostly in Bangkok and Nonthaburi, where 54 lung cancer patients had lived for same time were selected for investigating the presence of indoor radon by the charcoal canister method. In only four of these houses were radon level higher than the normal threshold level of 150 Bq.m (i.e. 153, 160, 172 and 283 Bq.m). Thus, the prevalence of elevated radon concentrations was a mere 7.40 percent in contrast with 22.16 percent found in the general survey. Although this finding would apparently suggest a negative relationship between indoor radon concentrations and lung cancer, it is possible that those patients had been exposed earlier to high radon concentrations, perhaps when the buildings were still new. It should be remembered also that exposure to even low radon concentrations dose not rule out the potential hazard of this radioactive gas as a cause of lung cancer. Most houses in this study (92.60%) were constructed of concrete and more than 5 years old. Therefore, it is not surprising to encounter such low radon levels, since rates are usually higher in newer buildings.

A preliminary study of indoor radon in Thailand.

A preliminary study of indoor radon was carried out at 176 sites in different buildings in Bangkok (n = 83), Nonthaburi (n = 79), Pathumthani (n = 7), Samutsakorn (n = 3), Samutprakarn (n = 2), and Nakornpathom (n = 2). Elevated radon concentrations were encountered in 19.28 per cent of the buildings in Bangkok and in 29.11 per cent of the buildings in Nonthaburi. Levels were not beyond the threshold in the four other provinces. The prevalence of buildings with elevated radon concentrations between Bangkok and Nonthaburi showed no statistically significant difference (P > 0.05). The arithmetic means and the standard deviations of the elevated concentrations were 226.31 +/- 81.95 Bq.m-3 for Bangkok and 417.96 +/- 455.27 Bq.m-3 for Nonthaburi. With regard to the age of the buildings, those less than five years old had a higher rate of elevated radon concentration when compared with buildings five or more years old (P = 0.60 = no statistical difference). There was evidence suggesting that poor ventilation might be a factor in the elevated concentrations of indoor radon.

Serum precipitins in pulmonary aspergillosis: preliminary results.

Definitive diagnosis of pulmonary aspergillosis is difficult to establish. Thus, confirmative evidence of active fungal aggression is imperative. In this study, an immunodiffusion test was carried out on 36 cases of pulmonary aspergillosis and two groups of subjects comprising 133 patients with non-fungal diseases and 134 healthy volunteers as controls. The test was positive in 92.3% of the patients with mycetoma, in 50% of the patients with allergic bronchopulmonary aspergillosis, and in 25% of the patients with invasive aspergillosis. Results were negative in all subjects in the two control groups. The findings indicate the efficacy of the test under study for supporting the diagnosis of pulmonary aspergillosis.

Dissertation of reported cases of nontuberculous mycobacteriosis in Thailand.

During the period from 1967 to 1988, there were 10 published reports of 44 patients from whom mycobacteria other than tubercle bacilli had been isolated clinic specimens. This communication presents results of a scrupulous review of each of the papers which revealed that some of the patients cited in the reports did not meet with the criteria for diagnosis, and some of the cases might have been the same patients as those documented by different investigators.

HLA antigen and ventilatory drive in Thais with chronic obstructive pulmonary disease.

Studies of HLA antigens in 15 Thai patients with chronic obstructive pulmonary disease revealed a significant increase in HLA-Bw 60 frequency in the group with low ventilatory drive to carbondioxide using unstimulated airway pressure. The finding suggests an immunogenetic role of HLA-Bw 60 on the control of ventilation in COPD.

Clinico-physiological status of Thai COPD patients.

We examined the relationships between certain clinical and physiological data from 56 patients with chronic obstructive pulmonary disease, and have formulated 15 relevant equations from which various respiratory indices can be estimated. Multiple linear regressions thus obtained evidently suggest that airway resistance and ventilatory drive are the main factors in the control of breathing among Thai COPD subjects; the exercise tolerance test showed some correlation with airflow obstruction and with respiratory muscle strength. Clinical implementation of certain findings has been outlined.

Ventilatory control, exercise tolerance and respiratory dysfunction in Thai COPD patients.

This study was designed to investigate a group of Thai COPD patients for their respiratory centre sensitivity while breathing room-air and during CO2 rebreathing, and tests to determine exercise tolerance and degrees of respiratory dysfunction. Results in 56 patients as compared with 45 age-matched healthy subjects disclosed comparable data between both subject groups, with the single exception that one-third (35.7%) of the patients experienced stronger ventilatory drive while breathing room-air and a lower musculo-ventilation transfer index during room-air breathing as well as CO2 rebreathing. According to the base-line dyspnoea index, the majority of Thai COPD patients in this study suffered from a very severe respiratory dysfunction, which correlated well with results of their basic physiologic tests.

Respiratory centre sensitivity and exercise tolerance in healthy Thais.

To determine the range of normal values of respiratory centre sensitivity and exercise tolerance in Thais, 69 healthy subjects, 18 to 72 years of age, participated in a series of tests, i.e. ventilatory drive, ventilatory response, musculo-ventilation transfer and the two-minute walking test with rating of the breathing sensation on a visual analogue scale. Our results showed higher end-tidal Pco2 and tidal volume response to CO2 and less exercise tolerance in the elderly than in the young. Only in young males was the ventilatory response to CO2 higher than in females. No attempt has yet been made to explain the lower ventilatory response in Thais as compared with Americans. Apparently, the defective respiratory apparatus, viz. increased airways resistance and not the blunting of respiratory centre sensitivity, contributes principally to relative hypoventilation and exercise limitation in the elderly. The compensation, with high tidal volume response to CO2, seems ineffective in maintaining normo-ventilation.

Oxygen desaturation during fibreoptic bronchoscopy.

One hundred consecutive patients, who underwent bronchoscopic examination for diagnostic purposes, were studied with regard to various aspects of possible SaO2 deterioration. Relevant findings are as follows: (1) The pulse oximeter is as good as the conventional blood gas analyser for quantitating SaO2; (2) oxygen desaturation in the range of 1 to 25 per cent (median 5, mean 5.6 +/- 4) occurred in approximately 97 per cent of the bronchoscopy examinees; recuperation time of SaO2 was 1 to 34 minutes (median 6, mean 8.2 +/- 6.5); (3) the factor aggravating desaturation included the examination of patients in the sitting position; the fact that bronchial washing was connected with greater SaO2 deterioration in the non-hypoxaemic group of patients needs further investigation with regard to its role in the mechanism of oxygen desaturation; (4) the amount of fluid instilled intra-tracheally, bronchial biopsy and duration of the procedure were not related to the decline in SaO2. Based on the results of the present study, the authors suggest that all procedures ought to be performed on patients undergoing examination in the supine position, and that the patients should be supplemented with low-flow oxygen.

The association of adenosine deaminase activity with T-lymphocytes and subsets in pulmonary tuberculosis and bronchogenic carcinoma.

Simultaneous determination of blood/lung ADA activity and T-lymphocyte subsets was conducted in 12 patients with active pulmonary tuberculosis, 12 patients with bronchogenic carcinoma and 11 healthy volunteers. Differences were significant only in the tuberculosis patients, namely, increased mean enzyme values in both the peripheral blood (36.68 +/- 10.90 U/L) and in the BALF (4.25 +/- 2.19 U/L), and correlation of ADA activity between the blood and the diseased lung only; the difference in elevated enzymatic activity between the tuberculosis group and the cancer group was of no statistical significance. We conclude that simultaneous ADA analysis of the blood and the BALF may be of diagnostic value in cases suspected of having tuberculosis as yet undiagnosed by other means. Based on the lowest value of enzymatic activity in the blood of patients with tuberculosis (28 U/L), the test has a sensitivity of 75 per cent and a specificity of 100 per cent; whereas the lowest value in the BALF of tuberculosis patients (2.9 U/L), the test has a sensitivity of 77 per cent and a specificity of 82 per cent. Findings that there was a blood-lung correlation of elevated ADA activity and a correlation of enzymatic elevation with increased numbers of T-cells bearing IL-2 receptor in cases of pulmonary tuberculosis only provide evidence in support of T-lymphocytes actively participating in the ongoing immune process.

Bronchoalveolar T-lymphocytes and subsets in pulmonary tuberculosis and bronchogenic carcinoma.

Analysis of T-lymphocytes and their subsets in the blood and bronchoalveolar lavage fluids from 12 patients with active pulmonary tuberculosis, 12 patients with bronchogenic carcinoma and 11 healthy volunteers was aimed at identifying their immunologic functions and interrelationships. In patients with active pulmonary tuberculosis, there was a significant increased in the percentage of T-cells bearing IL-2 receptor both in the blood and bronchoalveolar lavage fluids, whereas patients with bronchogenic carcinoma exhibited an increase in the suppressor T-cells and T-cells bearing IL-2 receptor in the blood only. The presence of T-cells bearing IL-2 receptor is generally accepted to be the hallmark of recently active specific antigen activation of the helper T-lymphocytes together with monokine IL-1 stimulation. Suppressor T-cells, on the other hand, play a role in the immunopathogenesis of lung cancers and lung metastasis.

Clinical assessment of respiratory impairment.

"Respiratory impairment" can be assessed roughly by clinical methods (symptom information and physical examination) and a simple bedside test ('match test'), and quantitatively and accurately by laboratory pulmonary function study (spirometry, arterial blood gas analysis and several other sophisticated tests). Whereas tests of respiratory impairment in a laboratory situation can predict dysfunction level reasonably well, a complete description of the function will depend in part on judgement, and in part on the motivation and attitude of the individual. Subject participation is an integral part of all evaluations.