Risk Mitigation for 1,3-Dichloropropene

Jing Tao Atac Tuli

Edgar Vidrio Pam Wofford

Randy Segawa

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1,3-D background

• 1,3-D is a pre-plant soil fumigant used for many pests

• 1,3-D is a restricted material – permit and certified applicator required

• Applied by tractor shank injection or through drip irrigation

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1,3-D background – crops

• Used prior to planting several crops

Soil Application

Strawberry Almond

Grapes

Uncultivated Ag

Carrots

Sweet Potato

Walnut

Raspberry

Tomatoes All Other Crops

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1,3-D background – 2014 use areas

• Use by township (6x6 mi area)

• Highest use in Central Coast and San Joaquin Valley

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1,3-D risk assessment

• DPR completed risk assessments in 1997 and 2015

Exposure Period 1997 Reference Concentration

(ppb)

2015 Reference Concentration

(ppb)

Acute (3 days) 35 110

Subchronic/seasonal (3 months) 25 3

Chronic (1 year) 25 2

Lifetime cancer risk (70 years)

0.014 (1x10-6 cancer risk)

0.056 (1x10-6 cancer risk)

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1,3-D risk management directive for cancer risk

• Goal is risk of no more than 1x10-5 (1 excess cancer in 100,000 people), consistent with

• 2001 risk management directive

• Prop 65

• U.S. EPA policy

Risk Management Directive Issue 2001 RMD 2016 RMD Goal for acceptable cancer risk 1x10-5 1x10-5

Exposure period 70 years 70 years Probability of acceptable risk 95% 95% Regulatory target concentration 0.14 ppb 0.56 ppb

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2002 Cancer mitigation measures – township cap program • Since 2002, mitigation measures include

• Use requirements within each township (6x6 mi area) – township cap

• Allocation of 90,250 lbs/yr, with unused amount “banked” since 1995

• Use limit of 180,500 lbs/yr, if available in bank

• Adjustment of allocations and use amounts based on application method, region, and month

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1,3-D township cap program for cancer risk

• 2002-2016 program is a 2-tier annual use limit to achieve 0.14 ppb regulatory target

• Beginning Jan 2017 program will be a single annual limit to achieve 0.56 ppb updated regulatory target

Program Element 2002-2016 2017 Annual allocation 90,250 adj lbs 136,000 adj lbs Annual maximum use 180,500 adj lbs 136,000 adj lbs Use adjustment factors 0.3x – 2.3x Unchanged Bank of unused allocation Yes No Application dates prohibited None December

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Township cap determined from air monitoring and use data

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Annual average 1,3-D concentrations • Calculated 31 annual average air concentrations (ppb) from

48 – 60 samples for each year and site (except Merced)

Site 2006 2011 2012 2013 2014 2015 Camarillo 0.091 Merced (9 sites, continuous)

0.535

Oxnard 0.191 0.167 0.089 0.207 Parlier 0.479 Ripon 0.308 0.050 0.195 0.067 0.084 Salinas 0.288 0.064 0.090 0.007 0.044 Santa Maria 0.165 0.192 0.189 0.112 0.109 Shafter 0.232 0.085 0.571 0.200 0.176 Watsonville 0.161 0.132 0.090 0.117

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Compiled annual use in 6x6 mi (township) area around monitoring site for all 31 site-year combinations

• Evaluated data for Jan – Dec and Jan – Nov

Higher air concentrations during December

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Determined air concentrations relative to use in 6x6 mile area • Used data without December (Jan-Nov)

• No correlation, so calculated ratio of concentration to use (ppb/adj lbs)

Site Year ppb Adj Lbs Ratio Percentile Shafter 2011 0.228 38,855 5.87x10-6 1.00 Parlier 2006 0.337 71,825 4.69x10-6 0.97 Ripon 2011 0.304 85,484 3.56x10-6 0.93 Shafter 2015 0.145 49,689 2.91x10-6 0.90 Salinas 2011 0.284 99,525 2.85x10-6 0.87 Oxnard 2015 0.207 76,100 2.72x10-6 0.83 Ripon 2012 0.047 18,253 2.55x10-6 0.80

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Township cap determined from 95th percentile of ratios and target concentration

• Calculated 95th percentile of ppb/adj lbs ratios = 4.12x10-6

• Calculated township cap using 0.56 ppb regulatory target concentration and 95th percentile ratio = 0.56 ÷ 4.12x10-6 = 135,785 adj lbs

• Township cap set at 136,000 adjusted pounds per year

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Summary of 1,3-D cancer risk mitigation

• Beginning Jan 2017

• Township cap will be 136,000 adjusted pounds each year

• Bank will be discontinued

• December applications will be prohibited

• Updated township cap program means that if

• 100,000 people lived in a 6x6 mile township for 70 years; and

• 136,000 adjusted pounds of 1,3-D were applied in the township every year for 70 years; then

• there is less than 5% chance that 1 person in the township would develop cancer from 1,3-D

Additional information and questions

• http://www.cdpr.ca.gov/docs/whs/1_3_d.htm

• Contact • Randy Segawa • 916-324-4137 • Randy.Segawa@cdpr.ca.gov

• Pam Wofford • 916-324-4297 • Pam.Wofford@cdpr.ca.gov

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