UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, DC 20460

			OFFICE OF  PREVENTION, PESTICIDES,  AND TOXIC SUBSTANCES

 

								9/25/07

MEMORANDUM

SUBJECT:		ENVIRONMENTAL FATE SCIENCE CHAPTER ON SODIUM FLUORIDE FOR RED
PROCESS

From:			A. Najm Shamim, PhD, Chemist

			Regulatory Management Branch II

			Antimicrobials Division (7510P)

To:			Timothy McMahon, PhD, Risk Assessor and Senior Toxicologist

			Antimicrobials Division (7510P)

					And

			Sanyvette Williams, D.V.M., CRM for Sodium Fluoride RED

			Antimicrobials Division (7510P)

Thru:			Mark Hartman, Chief

			Regulatory Management Branch II

			Antimicrobials Division (7510P)

ENVIRONMENTAL FATE ASSESSMENT OF SODIUM FLUORIDE:

EXECUTIVE SUMMARY

The Agency did not require and no fate data were submitted for sodium
fluoride. However, because sodium fluoride is used as a supplemental
wood preservative (non-pressure-treatment application) and in
agricultural settings as an inert, environmental fate assessment has
been made and to this end the Agency has conducted a published
literature search. There are not many studies published on environmental
fate chemistry of sodium fluoride.

A.	Hydrolysis:

	Sodium Fluoride is an inorganic substance which does not undergo
hydrolysis typically like an organic compound. Sodium fluoride is water
soluble and dissociates in water:

	NaF   ----------------->   Na+     +   F -       ------------------ (1)

 and further, fluoride  ion undergoes hydrolysis: F-   + H2O
--------------> HF + OH-    -----(2)

Because HF acid is a weak acid and OH ion is a strong base, it shifts
the pH to the alkaline side.

B.	Aqueous Photolysis:

	Sodium fluoride is transparent to ultra violet light and hence aqueous
photolysis is not likely to occur.

C.	Biodegradation Processes:

1.	A monitoring study reported in AWPA a showed that leaching of
supplemental wood preservatives (including sodium fluoride) from treated
wood poles indicated no ground water pollution with these supplemental
wood preservatives and the background level of fluoride ions is not
elevated.

2.	Surface water monitoring data showed that fluoride ion concentration
does not increase any higher than the concentration at the background
level.

	The background level in ground water does not exceed 0.4 ppm level
which is much lower than allowed in the drinking waters (0.7 ppm for
Southern United States and 1.2 ppm for the Eastern/Northern United
States).b Surface water also does not appear to be contaminated. Sodium
fluoride does not appear to pose any environmental concerns in surface
and ground waters.

b(Water and Wastewater Calculations Manual by Shundar Lin, pp 461-463,
McGraw Hill , 2001)

		

3.	Soil monitoring data from the same study showed an increase in the
concentration of fluoride ions up to 10 cm distance away from the pole
from which the wood preservative has leached out, but by the end of
study (18 months duration), the concentration of fluoride becomes equal
to the background levels. Most of the downward migration of fluoride
ions was up to 10 cm depth and is non-detect at 50 to 100 cm deep into
the ground around the poles. 

	NaF does not appear to be mobile in soil and slowly attains background
level concentrations.

	Sodium fluoride does not appear to adversely affect the soil biomass,
microflora and macro invertebrate of soil system.

	A monitoring study on wood preservative Osmoplastic was commissioned by
Osmose Wood Preserving, Inc. and conducted by Envirologic Data, Inc. of
Portland, Maine and Ground Water Technology, Inc. of Albany, New York,
and was completed in 1989. This study showed that if 100% of sodium
fluoride leached out into soil and all of it reached ground water (NaF =
400 ppm per release from one treated pole), the predicted concentration
of 1.44 mg/L would not exceed the Maximum Concentration  Limit (MCL) as
established by National Primary Drinking Water Act of EPA, 1988.

6	OPPT’s Modeling Program (EPI SUITE) estimated log Kow of sodium
fluoride = -0.77 and it being dissociating in aqueous medium, it is not
likely that sodium fluoride would be bioaccumulative.

Appendix

A Field Study of Mobility of Supplemental Wood Poles Preservatives in
Adirondack Wetlands

 (By: Edward M. Michalenko, Ph.D., Swiatoslav W. Kaczmar, Ph.D., and
Bryant A. Browne, Ph.D.) ( AWPA: Vol 97, 1993, pp 22-50)

	Empire State Electric Energy Research Corporation (ESEERCO) sponsored a
research project to conduct an environmental risk assessment on
supplemental wood preservatives used on utility transmission poles.
Moreover this study was conducted to evaluate eco and human health
impact of these wood preservatives. The study was performed by O’Brien
& Gere Engineers.

	Supplemental Wood Preservatives are used to arrest the ground line
decay of wood poles already in service and have been primarily treated
with existing pressure-treated preservatives.  Supplemental wood
preservatives are more cost effective than replacement poles.

	Field Site: New York State Adirondack Park was selected because it has
seasonally high water tables and nature of soil is sandy, which are
conducive to creating wetland environmental conditions and help in
environmental release and migration of the supplemental wood
preservatives. This in turn makes the detection of these wood
preservatives in soil and water easy. Supplemental Wood Preservatives
selected for this field study, along with their active ingredients are
shown in Table 1

						Table 1

Supplemental Wood Preservative Type/Treatment	Active Ingredients (
Reported as % by Volume)

Copper Naphthenate	Copper naphthenate (80%)

WoodFume ( Vapam)	Sodium methyldithiocarbamate(32.7%)

Dursban	Chloropyrifos (0.50%)

Hollow Heart	Sodium fluoride (10.9%), sodium dichromate (4.8%), sodium
arsenate (5.36%)

OsmoPlastic	Sodium fluoride (43.7%), creosote (40.0%), potassium
dichromate (3.1%), 2,4-dinitrophenol (2.0%)



	This review will extract and summarize data, analysis and conclusions
from the last two wood preservatives in Table 1 (OsmoPlastic, and Hollow
Heart) as these two contain sodium fluoride which is the subject of this
environmental fate assessment

	Methodology:

	

	A multilayer field study was conducted: 

1. Chemical Migration was monitored from the treated wood into the
nearby ground and surface water. This was done by collecting data
through four chemical sampling events.

	2. Soils were analyzed by conducting three chemical sampling events.

	3. Four biological sampling events were conducted to test for the
changes in soil respiration (any mineralization?), soil microbial
biomass (changes in microcosm), and soil-macro-invertebrates.

	4. Overall Sample Size of the Entire Study: 20 treated poles were
selected.

	5. Method of Application of the Supplemental Wood preservatives was:

		a. Ground line bandage treatment

		b. Internal treatment

		c. Internal fumigant treatment

	6.  Distribution of Wood Preservatives for Pole Treatments

	a.   In all 20 poles was selected for supplemental wood preservative
treatments. Of these nine were located in the Low lying areas (so-called
wetland area) and 11 in the so-called ‘upland’ areas.

	b.   Of the nine poles in the wetland area, three were treated with
copper naphthenate, three with Hollow Heart, and three with a mixture of
Osmoplastic, Dursban and WoodFume

	c.   Of these nine wetland poles, six contain sodium fluoride along
with other actives.

	d.   Of the 11 upland poles, three were treated with copper
naphthenate, three with the mixture of Osmoplastic, Dusrban, and
WoodFume and the remaining five were treated with Hollow Heart.

	e.   Of the 20 poles, 14 (wetland, upland) were treated with
ingredients containing sodium fluoride (70% of the poles).

	f.    Irrespective of the method of application each pole was treated
only once.

	Data Collections and Results:

	I. Ground Water Monitoring:

		1. In all 138 wells existed or created around these 20 poles. 

		2. Up to 8 wells existed around each poles

		

		3. Typically 4-5 poles were selected for ground water monitoring

4. O f these 3-4 poles were situated down gradient and 1-2 poles up
gradient with   respect to each pole.

	II. Chemical Monitoring:

Over a period of  eighteen months, four sampling events were carried out
at the rate of 4.5 months/event for both surface and ground water
monitoring. 

	For the same time period 3 monitoring events were conducted for soil
sampling.

	For both cases first monitoring sampling was done prior to supplemental
wood treatment.

Analyses of the water and soil samples were done using EPA Methods,
series 600 and 800, APHA, AWWA and WPDV Methods series 200, 300 and 700.


	III. Biological Monitoring:

Four sampling events were conducted for biological monitoring. First
sampling was carried out prior to the supplemental wood preservative
treatment.

	IV   Results of Ground Water Monitoring:

	For all poles ( 8) treated with Hollow Heart (containing sodium
fluoride), ground water monitoring results indicated  fluoride was
present  at the background level only and background level of fluoride 
determined in this area was between 0.15 to 0.4 ppm. Similarly, six
poles treated with Osmoplastic wood preservative (contains sodium
fluoride) and also Dursban (does not contain fluoride), did not show any
residues above the background level.

	V.  Results from Surface Water Monitoring:

	Fluoride ions were detected only at one pole, in both up gradient and
down gradient samples (in first, second, and third monitoring events) 
but at the background level only which was determined around this area
to be at 0.2 ppm In the fourth monitoring event, fluoride was
non-detect.

	VI. Soil Monitoring Results:

Soil sampling was done at two levels: 1) Surface and at 50 cm depth
around the pole, and 2) at, 10, 50 and 100 cm distance away from the
poles.

	a. 	Organic constituents of Osmoplastic were non-detectable in the soil
sampling. 

b. 	Fluoride ion was detected from all six poles treated with
Osmoplastic, Hollow heart and Dursban mixture treatments at the
background level of < 25 ppm. 

c. 	16/23 soil samples collected before the preservative application
showed the presence of fluoride ions.

	d. 	5/6 poles sampling at the 10 cm distance showed the presence of
fluoride ions between 9-29 ppm. The concentrations of fluoride ions
increased with time (second, third sampling events). Third soil sampling
event showed the presence of fluoride ions in all six Osmosplastic,
Dursban and Hollow Heart treated poles at a level of 13, 650, 180, 150,
and 63 ppm levels at a 10 cm distance away from the poles.  Beyond the
10 cm distance sampling, fluoride ion concentration attained the
background level.

	e. 	Deep soil sampling (50 cm deep, 10 cm away from the poles), the
concentration fluoride ions = 44 ppm. A second sampling event showed the
presence of fluoride ion between 20-100 ppm (at 10 cm distance away from
poles). Third sampling event showed (50 cm depth, and 10 cm distance
from poles) the presence of fluoride ions between 11-17 ppm.

	f. 	5/6 poles treated with Hollow Heart showed the presence of fluoride
ions above background levels. Background level fluoride ion
concentration in this are were between 2-110 ppm. However, no residues
of fluoride ions were detected at 50 and 100 cm distance away from the
treated poles. In general, above ground level residues of fluoride ions
were restricted to an area within 10 cm distance away from the treated
poles.

	VII: Biological Monitoring Results:

						

	 a. 	14 poles treated with OsmoPlastic, Dursban, Hollow HeartWoodFume,
and copper naphthenane were tested for soil respiration levels and no
sustained impact was noted in the soil respiration levels ( no increase
in carbon dioxide level was noted). 

	b. 	Soil micro flora was not impacted in the area around the treated
poles with all five supplemental wood preservatives.

	c. 	Soil samples from 15 supplemental wood preservatives were collected
and tested for soil-macro-invertebrates and no chemical impact was noted
on these samples.

	The duration of the entire study - chemical and biological monitoring
was 18 months.

	Conclusions:

	In general, organic and inorganic ingredients of the supplemental wood
preservatives when leached from the treated wood did not show any
chemical or biological impact in water, and soil around the treated
poles. Most of the constituents (including fluoride ions) did not
migrate more than 10 cm from the pole and not more than a 50 cm depth
around the poles. Most of the ingredients (including fluoride ions)
attained the background level concentrations by the fourth and last
monitoring event in soil and in ground water sampling most of the
ingredients were at the background level and in the surface water
sampling events, most of the ingredients were non-detectable.

	

Bibliography

	E. M.Michalenko et al., AWPA, Volume 89, 1993, pp22-50

	Handbook of Physics and Chemistry, 74th Edition

	Merck Index, 12 Edition

	Water and Wastewater Calculations Manual by Shundarin Lin, McGraw Hill,
2001, pp 461-463

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