Saf Health Work.  2015 Mar;6(1):18-24. 10.1016/j.shaw.2014.10.005.

Low-Oxygen Atmosphere and its Predictors among Agricultural Shallow Wells in Northern Thailand

• Wuthichotwanichgij G
• Geater AF

• KMID: 2317167
• DOI: http://doi.org/10.1016/j.shaw.2014.10.005

Abstract

BACKGROUND
In 2006, three farmers died at the bottom of an agricultural shallow well where the atmosphere contained only 6% oxygen. This study aimed to document the variability of levels of oxygen and selected hazardous gases in the atmosphere of wells, and to identify ambient conditions associated with the low-oxygen situation.
METHODS
A cross-sectional survey, conducted in June 2007 and July 2007, measured the levels of oxygen, carbon monoxide, hydrogen sulfide, and explosive gas (percentage of lower explosive limit) at different depths of the atmosphere inside 253 wells in Kamphaengphet and Phitsanulok provinces. Ambient conditions and well use by farmers were recorded. Carbon dioxide was measured in a subset of wells. Variables independently associated with low-oxygen condition (<19.5%) were identified using multivariate logistic regression.
RESULTS
One in five agricultural shallow wells had a low-oxygen status, with oxygen concentration decreasing with increasing depth within the well. The deepest-depth oxygen reading ranged from 0.0% to 20.9%. Low levels of other hazardous gases were detected in a small number of wells. The low-oxygen status was independently associated with the depth of the atmosphere column to the water surface [odds ratio (OR) = 13.5 for 8-11 m vs. <6 m], depth of water (OR = 0.17 for 3-<8 m vs. 0-1 m), well cover (OR = 3.95), time elapsed since the last rainfall (OR = 7.44 for >2 days vs. <1 day), and location of well in sandy soil (OR = 3.72). Among 11 wells tested, carbon dioxide was detected in high concentration (>25,000 ppm) in seven wells with a low oxygen level.
CONCLUSION
Oxygen concentrations in the wells vary widely even within a small area and decrease with increasing depth.

Keyword

agricultural shallow well; carbon dioxide level; confined space; Northern Thailand; oxygen level

MeSH Terms

Atmosphere*
Carbon Dioxide
Carbon Monoxide
Confined Spaces
Cross-Sectional Studies
Gases
Hydrogen Sulfide
Logistic Models
Oxygen
Soil
Thailand*
Water
Carbon Dioxide
Carbon Monoxide
Gases
Hydrogen Sulfide
Oxygen
Soil
Water