- Regular phosphorus fertiliser inputs (63?years) have significantly increased the amount of fluorine in the topsoil.
- Fluorine has moved and accumulated to a depth of least 50?cm in the soil.
- Fluorine movement wasn’t enhanced by irrigation but moved mainly in drainage after fertiliser application in mid-winter.
An understanding of the rate at which fluorine (F) accumulates in soil from phosphorus fertiliser and how much is lost via leaching are important because of the challenge elevated F may pose to soil, plant and animal health. This study measured F accumulation in a soil under pasture (Inceptisol) that received single superphosphate (SSP) fertiliser over 63?years in a long-term fertiliser trial. It also assessed the downward movement of F in soil and effect of irrigation in a long-term irrigation trial. Results showed total F concentrations in topsoil (0–7.5?cm) that received 188?kg SSP?ha?1 and 376?kg SSP?ha?1 fertiliser increased from 251?mg?kg?1 to 349 and 430?mg?kg?1, respectively. The rates of F accumulation were estimated at 1.1 and 2.1?kg?ha?1?yr?1 respectively, low compared to previous studies. The F concentration in the 376?kg SSP ha?1 treatment decreased with depth, but was significantly higher than the control treatment to 50?cm, suggesting movement of F down the soil. Fluorine concentrations also decreased with depth to 50?cm in soils that received either no irrigation or up to 770?mm?yr?1 from irrigation. However there was no significant difference in the amount of F with depth between irrigation treatments. We postulate that F was moving predominately in drainage water in the period immediately after P fertiliser application in mid-winter and wasn’t enhanced by irrigation. This study should be repeated for other soil types to help our understanding of the potential for ongoing F accumulation in soil and implications this may have on future land use.
Effects of fluoride toxicity on animals, plants, and soil health: a review.
Substantial multi-disciplinary efforts have been made to investigate the effects of environmental fluoride ion (F) pollution since the last century. The chronic ingestion of high doses of F may adversely affect human health by causing skeletal fluorosis, dental fluorosis, bone fractures, the formation of kidney stones, decreased birth rates, weakening
The safe exposure level to fluoride in pregnancy.
Three studies have now examined the safe exposure level to fluoride in pregnancy using benchmark dose analysis. In 2016, Hirzy et al. found that, for a benchmark response (BMR) of 1 IQ point, the lower confidence limit of the benchmark dose (BMDL) was a daily intake of approximately 0.27 mg/day,
Pharmacokinetic aspects of topical fluorides
Pharmacokinetic studies have revealed quantitative information about the bioavailability, rate of absorption, distribution, and clearance of fluoride following the use of fluoride-containing dentifrices, gels, varnishes, and solutions. It is concluded that following the use of topical fluoride products, variable amounts of fluoride are swallowed and absorbed into the systemic circulation--amounts which may be sufficient to produce acute
Total fluoride intake and excretion in children up to 4 years of age living in fluoridated and non-fluoridated areas.
Fractional fluoride retention is important during the early years of life when considering the risk of development of dental fluorosis. This study aimed to measure fractional fluoride retention in young children. The objectives were to investigate the relationships between fractional fluoride retention and total daily fluoride intake, age, and body
T for target organ, timing, and fluoride exposure.
Background: The brain is a main target organ for fluoride toxicity during early development. Based on recent epidemiological evidence, an approximate benchmark dose has been calculated for pregnant women at about 0.2 mg/L in water (or urine). This means that current limits for water-fluoride are too high, but tea has
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