ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 110 and 300 

National Oil and Hazardous Substances Pollution Contingency Plan 

U.S. Environmental Protection Agency (EPA) Proposed rule.

Dispersant Efficacy Testing and Listing Requirements

The current NCP Subpart J requires dispersants to be tested for saltwater efficacy in order to 

determine listing eligibility on the Schedule. Dispersant efficacy is tested following the Swirling 

Flask Test (SFT) protocol, which provides a relatively rapid and simple testing procedure for 

evaluating dispersant efficacy (i.e., the percentage of oil that is dispersed).

The Agency proposes to adopt the Baffled Flask Test (BFT) as the testing protocol for dispersant 

efficacy as described in the preamble of the proposed rule to reflect scientific advancements. The 

Agency also proposes revisions to the efficacy listing criteria for dispersants to be listed. 

Specifically, the dispersant must demonstrate that the lower 95% confidence level (LCL95) of 

six replicate flasks meets the new proposed efficacy listing criteria for two oils at two test 

temperatures. The proposal to test two new oils at two temperatures is intended to be 

representative of a wider range of oils that may be encountered and of locations where 

dispersants may be used.

The Agency initially tested eight of the dispersants currently listed on the Schedule with South 

Louisiana Crude following a BFT protocol consistent with the one proposed1. Three of the eight 

dispersants clearly differentiated themselves from the other five dispersants for having the 

highest LCL95 efficacy results. This natural break in the results provided the Agency with an 

approach to establishing a threshold criteria. 

For the proposed rule, the Agency tested a subset of those dispersants with the Alaska North 

Slope (ANS) and Intermediate Fuel Oil (IFO-120) oils at 5 °C and 25 °C to establish the efficacy 

thresholds. The ANS and IFO-120 oils were chosen as representatives of a light-medium and of a 

heavy oil, as described in Table 2 of the proposed Appendix C. Testing was conducted at 5 °C 

and 25 °C to be representative of the potential range of use conditions. The test results again 

showed a natural break in the efficacy of the products (see table below), which is the basis for 

the proposed threshold criteria. The proposed dispersant effectiveness (DE) values that 

dispersants considered must demonstrate for listing are as follow:

ANS at 5 °C: DELCL95 ≥ 70%

ANS at 25 °C: DELCL95 ≥ 75% 

IFO-120 at 5 °C: DELCL95 ≥ 55% 

IFO-120 at 25 °C: DELCL95 ≥ 65%.

1 Venosa, A.D., and Holder E.L., (2013) Determining the dispersibility of South Louisiana crude oil by eight oil 

dispersant products listed on the NCP Product Schedule, Marine Pollution Bulletin, Vol. 66, pp. 73–77

 
Comparison of Dispersant Effectiveness at 5 o

C and 25 oC with ANS and IFO120 oils. All tests conducted at 250 rpm.

Oil Temperature Dispersant Average Std. Dev. Variance

Coef. of 

Variation LCL95

ANS 5 Disperit SPC1000 90.12 2.88 8.31 3.20 87.75

5 Corexit 9500 79.57 5.37 28.85 6.75 75.15

5 JD2000 77.39 3.54 12.51 4.57 74.48

5 SafRonGold 59.35 3.44 11.82 5.79 56.52

5 ZI400 56.78 3.02 9.09 5.31 54.30

25 Disperit SPC1000 93.24 2.37 5.62 2.54 91.29

25 Corexit 9500 95.04 0.91 0.83 0.96 94.29

25 JD2000 81.01 3.17 10.05 3.91 78.40

25 SafRonGold 66.52 1.94 3.76 2.91 64.93

25 ZI400 61.64 2.10 4.41 3.41 59.91

IFO 120 5 JD2000 72.46 4.23 17.87 5.83 68.98

5 Disperit SPC1000 76.22 13.88 192.68 18.21 64.80

5 Corexit 9500 65.95 7.20 51.82 10.92 60.02

5 Nokomis 3AA 33.47 6.11 37.34 18.26 28.45

5 SafRonGold 23.57 2.86 8.20 12.15 21.21

5 ZI400 20.71 3.91 15.25 18.86 17.49

25 JD2000 84.10 6.62 43.86 7.88 78.65

25 Disperit SPC1000 81.37 8.84 78.18 10.87 74.09

25 Corexit 9500 77.39 6.80 46.22 8.79 71.79

25 Nokomis 3AA 66.76 6.87 47.17 10.29 61.11

25 SafRonGold 44.43 4.16 17.30 9.36 41.00

25 ZI400 43.88 5.27 27.74 12.00 39.55