Molecular formula: C₄H₆O₅
Molar mass: 134.09 g/mol
EINECS: 210-514-9 
Index of Refraction: 1.529
Density: 1.641 g/cm³
Flash Point: 153.4 °C
Enthalpy of Vaporization: 63.43 kJ/mol
Boiling Point: 306.4 °C at 760 mmHg
Vapour Pressure: 7.19E-05 mmHg at 25 °C
Melting point: 131-133 °C(lit.)
Water solubility: 558 g/L (20 °C)
Solubility: Methanol: 0.1 g/mL, clear, colorless
Appearance: White to nearly white crystals or crystal powder
Structure of Malic acid (CAS NO.6915-15-7):
                     
IUPAC Name: 2-Hydroxybutanedioic acid
Product Category of Malic acid (CAS NO.6915-15-7): Food & Flavor Additives

 Malic acid (CAS NO.6915-15-7) was first isolated from apple juice by Carl Wilhelm Scheele in 1785. Antoine Lavoisier in 1787 proposed the name acide malique which is derived from the Latin word for apple, mālum.

 Malic acid (CAS NO.6915-15-7) hasn't been listed as a carcinogen by NTP, IARC, ACGIH, or CA Prop 65. And the toxicological properties have not been fully investigated. You can see actual entry in RTECS for complete information.

Reported in EPA TSCA Inventory.

A poison by intraperitoneal route. Moderately toxic by ingestion. A skin and severe eye irritant. When heated to decomposition it emits acrid smoke and irritating fumes.
Hazard Codes: Xn,Xi
Risk Statements: 22-37/38-41-36/37/38 
R22:Harmful if swallowed. 
R36/37/38:Irritating to eyes, respiratory system and skin. 
R37/38:Irritating to respiratory system and skin. 
R41:Risk of serious damage to the eyes.
Safety Statements: 26-39-37/39-36 
S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. 
S36:Wear suitable protective clothing. 
S37/39:Wear suitable gloves and eye/face protection. 
S39:Wear eye / face protection.

 Malic acid , its cas register number is 6915-15-7. It also can be called DL-Hydroxybutanedioic acid ; and Malate . It is hazardous, so the first aid measures and others should be known. Such as: When on the skin: first, should flush skin with plenty of water immediately for at least 15 minutes while removing contaminated clothing. Secondly, get medical aid. Or in the eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Then get medical aid soon. While, it's inhaled: Remove from exposure and move to fresh air immediately. Give artificial respiration while not breathing. When breathing is difficult, give oxygen. And as soon as to get medical aid. Then you have the ingesting of the product: Wash mouth out with water, and get medical aid immediately. Notes to physician: Treat supportively and symptomatically.
In addition, Malic acid (CAS NO.6915-15-7) could be stable under normal temperatures and pressures. It is not compatible with excess heat, reducing agents, bases, alkali metals, and you must not take it with incompatible materials, excess heat. And also prevent it to broken down into hazardous decomposition products: carbon monoxide, carbon dioxide.