Classification of Red Phosphorus

1
Classification of Red Phosphorus
ECBI/09/00 Add 1

• Supplementary material for the application to
  classify red phosphorus as R52 (R53) Clariant
  GmbH, Sulzbach, Germany Dr. Adrian
  BeardItalmatch Chemicals S.p.A., Genova,
  Italy Dr. Silvestro Costanzi

2
What is the purpose of this presentation?

• summarize the documents submitted to ECB
• discuss any critical points
• come to a decision at the ECB meeting on
  25-Sep-2000
• on a revised classification of red phosphorus
• if no consensus can be found, then to decide
• whether further experiments and toxicity tests
  are necessary
• how any tests should be carried out
• (it is not the purpose to present new data)

3
Why is Red Phosphorus (RP) a special case?

• RP is a polymeric form of phosphorus
• RP usually contains traces (around 50 ppm) of
  white phosphorus (WP P4)
• RP is currently classified as R 50 / R 53 by
  analogy to white phosphorus
• new experimental data show that RP has very
  different environmental properties and should
  therefore be classified as less hazardous (R 52)
• as a polymer RP is not soluble in water
• structure of RP versus WP

4
Properties (backup slide)
5
Red Phosphorus Reactions in Water (1)
schematic overview of likely reactions
white phosphorus (P4, max. 200 mg/kg)
red phosphorus, amorphous polymer
1
2
3
4
OH
H3PO2X
H3PO3
H3PO4
H
X
no spontaneous dissolutionof yellow P
Reactions
6
Red Phosphorus Reactions in Water (2)

• RP slowly reacts with water and dissolved oxygen
  lt 3 of RP react within 4 months (at a loading
  of 10 g/L)
• main products are traces of phosphine and oxyacids

Red Phosphorus Hydroylsis Products - Yield
3.0
2.0
total Phosphorus in solution, based on input
1.0
0.0
0
20
40
60
80
100
120
Time d
7
Aquatic Toxicology of Red Phosphorus
classification
results for red phosphorus after 24 h hydrolysis
LC50, EC50 mg/L
GermanWGK
fish gt 100 mg/Lalgae gt 100 mg/L
100
R 52, (R 53)
1
daphnia 36 mg/L
10
R 51, (R 53)
2
1
N, R 50, (R 53)
2
based on nominal loading rates, the sample
tested contained 50 mg WP / kg WGK
Wassergefährdungsklasse, water hazard class
8
What determines the aquatic toxicity of Red
Phosphorus?

• experimental data indicate that it is not the
  white phosphorus
• on extraction of RP with water one does not find
  WP in the water
• after aqueous extraction of RP the content of WP
  is unchanged
• the hydrolysis products of red phosphorus form
  the toxic agent
• it is not clear which of the products yields the
  toxic effects -not all products could be
  identified
• it would be nice to know the exact chemical
  species and mechanism of toxic action, but for
  classification the toxic effects only need to be
  determined quantitatively

9
Why was a nominal loading rate approach applied?

• in analogy to established concepts of water
  accomodated fraction for sparingly soluble
  substances and water-soluble fraction
• the media were filtrated to avoid physical
  effects of fine particles on the test organisms
  ? water-soluble fraction

10
Why was a hydrolysis time of 24 hours chosen?

• the acute toxicity is to be tested
• OECD testing of difficult substances
• Half-life gt3 days gt test parent substance (not
  the hydrolysis products)
• EN ISO 5667-161998 Water quality - Sampling -
  Part 16 Guidance on biotesting of samples
  chapter 10.1.7
• mentions a 24 h hydrolysis time
• German guidance document on the classification of
  substances that are hazardous to the aqueous
  environment (LTwS-Nr. 10, ch. 3.6)
• Half-life gt12 hours gt test parent substance
• 24 h are common time to prepare water-soluble
  fractions of oil-based products (Girling, 1989)
• longer term effects are covered by R53

11
Which scenario was chosen for toxicity testing?

• a 24 hour hydrolysis represents appropriate
  conditions for short term toxicity testing
• longer hydrolysis times lead to more hydrolysis
  products in solution and possibly higher
  toxicity, but these longer term effects are
  covered by R53
• other test conditions are also not worst case
  (often due to experimental considerations), e.g.
• decanting surface films,
• letting emulsions settle or
• filtration of particulates
• do not necessarily happen in the environment

12
Why is a static toxicity test sufficient?

• the total concentration of phosphorus species was
  measured at the beginning and end of the tests -
  they were found to have remained fairly constant
  (p. 22 Daphnia test)
• when very slowly reacting soluble substances are
  tested, static tests may be used also
• therefore, we see no need for a semi-static test

13
The influence of pH on the hydrolysis of RP

• only a pH-range which is representative and
  realistic for the aquatic environment should be
  considered pH 6 ... 8.5
• the rate of hydrolysis increases with increasing
  pH values
• pH values of toxicity test waters covered the
  range of 7.5 ... 9

14
The content of White in Red Phosphorus (Clariant)

• Clariant statisticsbased on 59 samples
• November 1996 - April 2000
• average value 38.6 mg/kg

Histogram WP in RP, Clariant
12
120
of samples
10
100
8
80
number of samples
6
60
4
40
2
20
0
0
10
20
30
40
50
60
70
80
90
100
110
120
130
White Phosphorus mg/kg
15
The content of White in Red Phosphorus (Italmatch)

• Italmatch statistics based on 140 samples
• Nov.1996 - Jul. 2000
• average value 49.9 mg/kg

16
Should the labelling of Red Phosphorus be tied to
maximum concentration of White Phosphorus?

• it is difficult to prepare RP with a defined,
  high WP content (200 ppm)
• in preparations, T-labelled compounds are
  allowed up to 0.1 (1 000 ppm) without a
  provision to label accordingly
• 98 of RP samples have lt 0.01 WP
• there are strong indications that the aquatic
  toxicity of RP is not due to released WP but
  caused by hydrolysis products of RP

17
Is the R 53 label (long term effects) justified?

• red phosphorus is an inorganic polymer
• it reacts very slowly in the aquatic environment
  via disproportionating, hydrolysis and oxidation
  without reaching an equilibrium for months
• because there is no indication that the toxicity
  of the reaction products declines quickly, R 53
  seems justified