2

RR Case Name PC Codes

Calcium Hydroxide 075601 1305-62-0

CAS #

Calcium Oxide 075604 1305-78-8

TABLE OF CONTENTS 

CALCIUM HYDROXIDE/ CALCIUM OXIDE..................2

APPENDICES-------------------------------------------------------------10

REGISTRATION REVIEW DOCUMENT

PRODUCT CHEMISTRY, ENVIRONMENTAL FATE AND

ECOLOGICAL EFFECTS SUMMARY FOR CALCIUM HYDROXIDE AND 

CALCIUM OXIDE

Important Note on the Chemistry of Calcium Hydroxide and Calcium Oxide:

Calcium oxide (CaO) dissociates: Ca+2 + O2- Oxide ion is a basic entity, as when water 

is added to calcium oxide, the oxide ion reacts: O2- + H2O ----- 2OH- and Calcium 

hydroxide dissociates: Ca+2 + 2OH- Thus the chemistries of calcium oxide and 

hydroxide complement each other and the major entities present in aqueous medium or 

soils are three: calcium ions, oxide which in moist soil converts to hydroxide, and 

hydroxide from calcium hydroxide. In water the presence of these entities increases the 

water hardness, and alkalinity; and pH of acidic soil increases due to the presence of 

hydroxide; calcium ion is ubiquitously present in the environmental media like water and 

soils. When heated calcium hydroxide converts into calcium oxide in the absence of air; 

in the open atmosphere, calcium hydroxide converts into calcium carbonate, another 

basic entity, but less corrosive than calcium oxide or calcium hydroxide

PCCode: 075601/ 075604 Case No. 4065/4066

Chemical name Use patterns/use sites

Cold-Ster/Calcium Oxide Treatment of Medical Waste

Hydrated Lime(Calcium Hydroxide) MUP*

* Other use sites listed on the MUP label are:

Paint film or coatings on inanimate surfaces, tools, walls, ceilings, floors, appliance 

exteriors, pipe exteriors, HVAC equipment, duck works, and other related equipment (not 

including: motors, fans and other moving mechanical parts)concrete, stones, ceramics, 

plastic, wood, , interiors, and exteriors, dry wall substrates in residential dwellings, 
3

schools, day care centers, professional offices, commercial and industrial buildings, 

factories, animal housing, facilities (barns, corrals, fences)and health care facilities, 

hospitals, medical offices, and nursing homes. Applications to interior surfaces of HVAC 

system should be made during construction, assembly, or installation of the unit and 

during the period when the HVAC system is not in operation, and the building is 

unoccupied. The product is not for use in or on coatings and other antimicrobial pesticide 

that will be used on food contact, food preparation, or food processing surfaces.

These chemicals were first registered by EPA in 1988. At present they are registered for 

use as baceteriocide/ bacteriostat and use for medical waste treatment. Over the years 

calcium hydroxide has been approved for Section 18 registrations to control Coqui and 

green house frogs in outdoor plants in nurseries and residential areas, parks, hotels and 

resorts, forest habitats, and natural areas in Hawaii (2004, 2008, 2010).

Regulatory History:

Table 1: Registered Active Products for Calcium Hydroxide

EPA Reg. 

Number

Product Name Formulation 

Type

% Active 

Ingredient

Registrant

73696-2 Hydrated Lime Powder/MUP 96.6 Alistagen Corporation

75661-1 Cold-Ster Powder 86.8 Positive Imapct Waste 

Solutions, LLC

Table 2A. Chemical Identity 

Common Name Hydrated Lime

Chemical Name Calcium Hydroxide

IUPAC Name Calcium Hydroxide

Molecular Weight 74

PC Code 075601

CAS Registry Number 1305-62-0

Molecular Formula/Empirical 

Formula

Ca(OH)2

Registration Review Case No. 4065

Registration Review Case Name Calcium Hydroxide

Classification: Inorganic
4

Table 2B. Chemical Identity 

Common Name Calcium Oxide/slaked lime

Chemical Name Calcium Oxide

IUPAC Name Calcium Oxide

Molecular Weight 56.0

PC Code 075604

CAS Registry Number 1305-78-8

Molecular Formula/Empirical 

Formula

CaO

Registration Review Case No. 5104

Registration Review Case Name Calcium Hydroxide/Calcium Oxide

Classification: Inorganic

Structures: 

OHCa+2 

OHCa+2 O2-

Science Findings:

Following tables summarize the science data for each discipline, and lists some possible 

data gaps.

Product Chemistry Summary

Table 3A: Physical and Chemical Properties of Calcium Hydroxide

Guideline 

No.

Physical and Chemical Properties Value

830.1550 Product identity and composition Refer to Table 2

830.1600 Description of materials used to 

produce the product

Cbi

830.1620 Description of production process Cbi

830.1650 Description of formulation process Cbi

830.1670 Discussion of formation of impurities Cbi

830.1700 Preliminary analysis Cbi

830.1750 Certified limits Cbi

830.1800 Enforcement analytical method Cbi
5

Guideline 

No.

Physical and Chemical Properties Value

830.1900 Submittal of samples Cbi

830.6302 Color white: MRID: 45266603

830.6303 Physical State solid; MRID 45266603

830.6304 Odor Odorless: MRID: 45266603

830.6313 Stability to sunlight, normal and 

elevated temperature

Stable under normal temperature and pressure; 

decomposes to calcium oxide at 580 o C through 

loss of water

830.6314 Oxidation/Reduction: Chemical 

Incompatibility

Readily absorb CO2 from air forming calcium 

carbonate; incompatible with maleic anhydride, 

phosphorous, nitroethane, nitrormethane, 

nitropariffins, nitropropane; all can form explosive 

salts with calcium hydroxide

830.6315 Flammability

Flash Point

NA

830.6316 Explodability NA

830.6317 Storage Stability Waiver requested; MRID: 45266603

830.6319 Miscibility NA

830.6320 Corrosion Characteristic Calcium hydroxide forms a corrosive solution with 

a pH of 12-12.49 when combined with water

830.6321 Dielectric breakdown voltage NA

830.7000 pH 12.4 at 25 o C

830.7050 UV/Visible absorption spectra CaO stretch 591-9 cm-1

830.7100 Viscosity NA

830.7200 Melting Point Calcium hydroxide does not a true melting point 

at 580 o C calcium hydroxide loses water and 

converts to calcium oxide

830.7220 Boiling point It does not have a true BP, as it converts to CaO at 

its MP.

830.7300 Density/ Bulk density 2.24 g/cc o C2

830.7370 Dissociation Constants in water Calcium hydroxide in aqueous solution at 25 o C1

Is a strong base with a pKb < 0

830.7520 Particle size NA

830.7550 Octanol/water partition coefficient 

(KOW) (Log Kow )

NA

830.7840 Solubility in water 1730 g/L at 20 0 C; 0.185 g/100 ml at 0 o C; 0.077 

g/100 ml at 100 o C

830-7840 Solubility in organic solvents in g/100 

ml

NA

830.7950 Vapor pressure It is a solid, vapor pressure is likely negligible
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Table 3B: Physical and Chemical Properties of Calcium Oxide

Guideline 

No.

Physical and Chemical Properties Value

830.1550 Product identity and composition Refer to Table 2a

830.1600 Description of materials used to 

produce the product

Cbi

830.1620 Description of production process Cbi

830.1650 Description of formulation process Cbi

830.1670 Discussion of formation of impurities Cbi

830.1700 Preliminary analysis Cbi

830.1750 Certified limits Cbi

830.1800 Enforcement analytical method Cbi

830.1900 Submittal of samples Cbi

830.6302 Color Grayish white: MRID:46052702

830.6303 Physical State solid; MRID 46052702

830.6304 Odor Odorless: MRID: 46052702

830.6313 Stability to sunlight, normal and 

elevated temperature

Stable under normal temperature and pressure; 

decomposes to calcium oxide at 580 o C through 

loss of water

830.6314 Oxidation/Reduction: Chemical 

Incompatibility

Calcium oxide reacts with water to form calcium 

hydroxide and heat is evolved. It reacts violently 

with chlorine trifluoride and phosphorous 

pentoxide; MRID# 46052702

830.6315 Flammability

Flash Point

NA: MRID# 46052702

830.6316 Explodability NA: MRID#: 46052702

830.6317 Storage Stability Calcium oxide is stable if stored in tightly closed 

plastic containers. CaO readily absorbs carbon 

dioxide and water from air to become slaked. 

MRID#: 46052702

830.6319 Miscibility NA: one gram of CaO is slightly soluble in 840 

ml/water: MRID: 46052702

830.6320 Corrosion Characteristic Calcium oxide will possiblye become corrosive to 

aluminum when the chemical becomes wet.: 

MRID#: 46052702

830.6321 Dielectric breakdown voltage NA

830.7000 pH 12.5 ; MRID#: 46052702

830.7050 UV/Visible absorption spectra CaO stretch 591-9 cm-1 MRID#: 45266603

830.7100 Viscosity Not applicable

830.7200 Melting Point No Report

830.7220 Boiling point No Report

830.7300 Density/ Bulk density 3.2-3.34 g/cc MRID#: 56052702

830.7370 Dissociation Constants in water Not applicable

830.7520 Particle size No Report

830.7550 Octanol/water partition coefficient 

(KOW) (Log Kow )

Not applicable

830.7840 Solubility in water 1730 g/L at 20 0 C; 0.185 g/100 ml at 0 o C; 0.077 

g/100 ml at 100 o C; MRID#: 46052702

830-7840 Solubility in organic solvents in g/100 

ml

No Report

830.7950 Vapor pressure It is a solid, vapor pressure is likely negligible
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Environmental Fate and Transport Data Summary:

The environmental fate test guidelines (161 series) are not applicable for calcium oxide 

or calcium hydroxide. 

Calcium hydroxide and Calcium Oxide in environmental media:

In water: Calcium hydroxide is slightly soluble in water, ~ 0.15 g/100ml; in solution 

calcium hydroxide consists of: calcium ions, hydroxyl ions, with approximate pH of 12.4; 

when acid is added, more calcium hydroxide dissolves. In water then, calcium hydroxide 

tends to increase the water hardness, and alkalinity. When base OH is added, calcium 

precipitates more. When heated, it interacts with atmospheric carbon dioxide to form 

insoluble calcium carbonate. When heated solid calcium hydroxide forms calcium oxide.

Calcium oxide is a solid, and interacts with water violently to form calcium hydroxide, 

and large amount of heat is produced. As a solid calcium oxide contains calcium ions,

and oxide ions.

In acidic soils: calcium oxide will increase the pH of soils by replacing aluminum 

through cation exchange. In most acidic soils, calcium oxide would first convert into 

calcium hydroxide and then liming process (raising the pH of acidic soils) would follow.

Depending on the nature of soils, and selected crop(s) each state will have a specific 

recommendations for a defined capacity of calcium hydroxide required for liming process 

for soils.

Environmental Fate and Transport Conclusions:

No long term environmental impact is expected from calcium hydroxide or calcium 

oxide in water and soils from present use and use patterns.

Environmental Fate and Transport Data Gaps

No environmental fate data gaps exist for calcium hydroxide or calcium oxide for the 

present uses of these chemicals, and the Agency does not anticipate requiring any 

additional fate data.
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Ecological Effects Data Summary:

Table 4 summarizes the eco-toxicity data that AD has either in its data base or collected 

from open literature. The studies were conducted with calcium hydroxide . These studies 

provided some information to characterize toxicity, but they were not reviewed and do 

not fulfill the data guidelines.

Table 4

 Ecotoxicity Data

Guideline #/Study 

type

MRID#/Reference 

Information/Study 

Classification

Dosing/Organism 

Information

Results

850.1075: Fish 

Acute Toxicity Test 

( Zambezi Barbel) 

African Catfish

MRID#: 45266613:: 

Aquacult Fish 

Management; Vol 

21, pp 181-185

Ca(OH)2 administer 

for 96 hours at 

10,20, 40, 80, 150 

mg/L; purity not 

reported

96-hour LC50: 34 

mg/L

850.1075: Fish 

Acute Toxicity 

(Western Mosquito 

fish)

MRID 45266614:. 

Sewage and 

Industrial Wastes 

29(6):695-711

Ca(OH)2

administered for 96 

hours; purity not 

reported

96 hour LC50: 160 

mg/L

Invertebrate: Scud Open Literature: 

Yee et al. (2000)

Ecotox Reference 

90867

Administered for 96 

hours; dosing not 

reported

96 hour 

NOAEC(mortality): 

1188 mg/L; 

practically non-toxic

Invertebrate: Midge Open literature; Yee 

et al.(2000); Ecotox 

Reference 90867

Administered for 96 

hours; dosing not 

reported

96 NOAEC 

(mortality): 1781 

mg/L; practically 

non-toxic

Aquatic Plants: 

Blue-green Algae

Open Literature:

Ecotox Reference 

15018

Method of 

administration not 

reported

EC50: 66 mg/L

Terrestrial Animals: 

Red-winged 

Blackbird

Open Literature: 

Richardson & 

Gangoli(1993)

Method of 

administration not 

reported

LD50 = 111 mg/kg; 

moderately toxic

Mammals: Rat Richardson & 

Gangoli (1993)

Method of 

administration not 

reported

LD50= 7340 mg/kg; 

practically non-toxic

Invertebrates: 

Earthworm

Diaz-Lopez and 

Mancha (1994)

Ecotox Reference 

40516

48 hour LC50 LC50= 520μg/cm2
9

Note: A number of studies listed in Table 4 are referenced in the section 18 (Emergency 

use of calcium hydroxide granted to Hawaii by the Agency); no ecotoxicity or fate 

assessment were carried for this use. Some of these ecotoxicity studies were conducted 

on species that are not native to USA.

Ecotoxicity Conclusions :

The ecotoxicity studies in its database listed in Table 4 for calcium hydroxide appear to 

be nontoxic to: western mosquito fish, slightly toxic to African catfish, which is not 

native of USA; non-toxic to invertebrates like scud, and midge; for aquatic plant like 

blue-green algae only inhibition of nitrogen fixation is observed; it is moderately toxic to 

red-winged blackbird. These studies provided some information to characterize toxicity, 

but they were not reviewed and do not fulfill the data guidelines. These studies were not 

reviewed or assessed. The Agency is requiring the following studies and anticipates to 

conduct the risk assessment based on the available studies and the additional studies that 

the agency requested by the Agency

Ecotoxicity Data Gaps:

Since the ecotoxicity data was generated on non-guideline studies, as well as the fact the 

species on which the studied were conducted are not native to USA, the Agency is

requiring the following ecotoxicity studies:

850.1075 Acute freshwater fish toxicity

850.1010 Acute Toxicity Freshwater invertebrate

850.5400 Aquatic growth, Tier II green algae
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APPENDIX A

Data justifications for ecotoxicity of Calcium Hydroxide

Guideline Number: 850.5400

Study Title: Algal toxicity (Tier II)

Rationale for Requiring the Data

As part of a Tier I risk assessment, one indicator plant species is tested for phytotoxicity. This study 

would allow the Agency to categorize barium calcium hydroxide/calcium oxide as toxic or non-toxic 

to plants. If toxic, additional higher tier plant tests would be needed. An endangered species 

assessment for endangered or threatened plants is not possible without this study.

Practical Utility of the Data

1. How will the data be used?

This study would be used to evaluate the toxicity of calcium hydroxide/calcium oxide to non-target 

plants in terrestrial and aquatic ecosystems.

2. How could the data impact the Agency’s future decision-making?

Adverse effects to non-target plants in terrestrial and aquatic ecosystems may result in mitigation to 

protect species at risk. Mitigation might include reduced label dosages, neutralization of effluents prior 

to discharge into water, restrictions on use in sensitive ecosystems or where endangered species are 

present, or other mitigation measures.

3. What is triggering the need for this data?

Increased concern from state regulators and the public to evaluate impacts on WWTP operations, 

endangered species, and persistence in the environment, since initial registration, have triggered the need 

for this study. Green algae are critical to ecosystem health and productivity.
11

Guideline Number: 850.1075

Data Requirement: Acute Fish Toxicity (estuarine/marine)

Rationale for Requiring the Data

Sport fishing and commercial fishing have a high impact on the United States economy. The acute 

toxicity tests with estuarine/marine fish are designed to measure mortality during short-term (96-h) 

aquatic exposure to a range of concentrations of the pesticide in water. The preferred test species is 

Atlantic silverside (Menidia menidia) for salt water.

Practical Utility of the Data

1. How will the data be used?

Data would be used to determine concentration-response curves and calculate LC50's (with 95% 

confidence intervals) for 24, 48, 72, and 96 h. Additionally, a NOEC for 96 h is reported. The 

results from these studies may also provide information for a concentration-selection rationale for 

fish early-life stage study (OPPTS 850.1400) and the fish life cycle study (OPPTS 850.1500).

2. How could the data affect the risk assessment?

There are many estuarine/marine fish species that are listed as threatened and endangered in the 

United States. Although the Atlantic silverside is the preferred species, the sheepshead minnow is 

considered a surrogate species to represent all marine/estuarine fish species in the risk assessment 

process. As part of the acute risk assessment for aquatic animals, the lowest EC50 or LC50 for 

estuarine/marine fish is used in the RQ equation. An acute RQ > 0.5 would indicate an acute LOC, 

defined as the potential for acute risk to non-target organisms which may warrant regulatory action 

in addition to restricted use classification. An acute RQ > 0.1 would result in an acute restricted use 

LOC, defined as the potential for acute risk to non-target organisms, which may be mitigated 

through restricted use classification. An acute RQ > 0.05 would fall under the LOC for acute 

endangered species.

3. What is triggering the need for this data?

Data are needed in order to conduct an ecological risk assessment for the proposed use of calcium 

hydroxide/calcium oxide and determine the acute toxicity of calcium oxide to estuarine/marine fish.
12

BIBLIOGRAPHY FOR: PRODUCT CHEMISTRY, ENVIRONMENTAL FATE

AND TRANSPORT, AND ECO-EFFECTS 

1. MRID#: 45266603

2. MRID#: 46052702

3. A Memo by A. Najm Shamim to Norm Cook, Chief RASSB in AD (Feb 01, 

2001) (DPBarcode: D272177(S590169) On the Chemical Screening of 

Calcium Hydroxide

4. Section 18 Memo From Colleen Flaherty to Dan Rieder, Chief Environmental 

Risk Branch 3, Dec. 2004, EFED

5. Section 18, A Memo From Colleen Flaherty to Tom Bailey, Branch Chief, 

EFED, June 2008

6. Diaz-Loez et al., 1994: Ecotoxicity of Soil Organisms, Lewis Publ, Boca 

Raton, Florida: pp 251-256

7. Peterson et al., 1995: Water Research, volume 29(6), pp 1515-1523

8. Richardson, et al., 1993: The Dictionary of Substances and their Effects. 

Royal Society of Chemistry, UK

9. Ufodike, et al, 1990: Aquatic Fish Management, volume 2(2), pp 181-185

10. Yee et al., 2000: Canadian Journal of Fish & Aquatic Science: 57: 125-136