USE OF PYRETHRIN/ PYRETHRUM AND ITS EFFECT ON ENVIRONMENT AND HUMAN: A REVIEW

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About Authors:
Vishal Soni*, Amruta Anjikar

CSIR-National Environmental Engineering Research Institute (NEERI),
Nagpur, Maharashtra
vishalsoni8912@yahoo.com

Abstract:
Pyrethrins and pyrethrum are the most frequently used home and garden insecticides in the India. They are often used in indoor sprays, pet shampoos, and aerosol bombs to kill flying and jumping insects. Pyrethrins are a common cause of insecticide poisonings. According to Ministry of Environment and Forest survey of poison control centers, they cause more insecticide poisoning incidents than any other class of insecticides except the organophosphates. Symptoms include headaches, dizziness, and difficulty breathing. Pyrethrins can trigger life-threatening allergic responses including heart failure and severe asthma. In laboratory animals exposed through eating, by injection, or through breathing, pyrethrins have caused anemia. Experiments with dairy cows suggest that nursing mothers exposed to pyrethrins can pass them on to their children. Pyrethrins disrupt the normal functioning of sex hormones. They inhibit binding of sex hormones to human genital skin and proteins in human blood. Pyrethrins are classified as “likely to be human carcinogens” by Environmental Protection Agency (EPA) because they cause thyroid tumors in laboratory tests. Farmers who use pyrethrins have an increased risk of developing leukemia. Pyrethrins are extremely toxic to bees, fish, and other aquatic animals. Following indoor treatments, pyrethrins have persisted up to 2 1/2 months in carpet dust.

REFERENCE ID: PHARMATUTOR-ART-2178

PharmaTutor (ISSN: 2347 - 7881)

Volume 2, Issue 6

Received On: 04/04/2014; Accepted On: 10/04/2014; Published On: 01/06/2014

How to cite this article: V Soni, A Anjikar; Use of Pyrethrin/ Pyrethrum and its Effect on Environment and Human: A Review; PharmaTutor; 2014; 2(6); 52-60

Introduction:
Pyrethrum is the generic name given to a plant based insecticide derived from the powdered, dried flower heads of the pyrethrum daisy, chiefly Chrysanthemum cinerariaefolium, but also in C. coccineum and C. marshalli. Pyrethrins are the six constituent compounds with insecticidal properties that occur in these Chrysanthemum species. Be careful not to confuse pyrethrum with pyrethrin. Pyrethrin refers to a more refined extract of pyrethrum.1 Pyrethrins are the six insecticidal active compounds in pyrethrum. You will often find pyrethrum mixed with a synergist such as piperonyl butoxide (PBO). PBO gives pyrethrum an added "kick" that makes it more effective against insects.


Figure 1: Structure of Pyrethrin

Use of Pyrethrum:
Pyrethrum is used widely throughout the world to control many human and household pests such as mosquitoes and houseflies. While it was used widely in agriculture before World War II, cheaper and more effective synthetic products have mostly replaced it for farm use.4More recently, new pyrethrum products, often solvent-based and including PBO, have appeared on the agriculture market.7 Other than home and garden uses, pyrethrins are used on a variety of agricultural crops and for structural and public health pest control. Worldwide, about 200,000 kilograms (440,000 pounds) of pyrethrins are used each year.6

Mode of Action:
Pyrethrum induces a toxic effect in insects when it penetrates the cuticle and reaches the nervous system. The pyrethrins that compose pyrethrum bind to sodium channels that occur along the length of nerve cells. Sodium channels are responsible for nerve signal transmission along the length of the nerve cell by permitting the flux of sodium ions. When pyrethrins bind to sodium channels, normal function of the channels is obstructed thereby resulting in hyper excitation if the nerve cell and, consequently, a loss of function of the nerve cell.9The shutdown of the insect nervous system and insect death are most often the consequences of insect exposure to pyrethrins. The commercially available combination of pyrethrins (0.17-0.33%) and piperonyl butoxide (2-4%) seems to be safe when applied to the skin in a non aerosol product.10

Hazards of Inert Ingredients:
Propane
is used as an inert propellant in pyrethrin products. It can cause dizziness when inhaled. It is also “extremely flammable” and easily ignited by heat, sparks, or flame.2

Isobutene is also used as an inert propellant in pyrethrin products. It depresses the central nervous system and can cause dizziness when inhaled. Like propane, it is extremely flammable and easily ignited.4

Hydro treated light petroleum distillates (hydro treated kerosene) are used as an inert solvent in pyrethrin products. The Chemical Abstract Services number for this solvent is 64742-47-8. This solvent has caused skin tumors when applied to the skin of laboratory mice.6

Hydro treated heavy naphtha (white spirits) is also used as an inert solvent in pyrethrin products.1The Chemical Abstract Services number for this solvent is 64742-48-9. It is damaging to kidneys and the nervous system.8In a recent laboratory study, the offspring of animals exposed to white spirits developed “long-lasting and possibly irreversible changes” in brain cells. This damage to the brain was caused by an inability to maintain normal calcium concentrations.9

Toxicological Information:

Pyrethrum (as 100%):
Acute Oral Toxicity LD50 (rat) = 3500 mg/kg
Acute Skin Toxicity LD50 (rabbit) = >19000 mg/kg

Piperonyl Butoxide (as 100%):
Acute Oral Toxicity LD50 (rat) = 6150 mg/kg
Acute Skin Toxicity LD50 (rabbit) = 1880 mg/kg

How safe is Pyrethrum?
Pyrethrum has been extensively studied for its effects on people and the environment. Like all insecticides, pyrethrum is used to have a toxic effect on insects. Thus it is not correct to say that pyrethrum is "safe." At the same time, we are confident that pyrethrum has a very good toxicity profile.5For mammals, doses that elicit toxic reactions are significantly larger than the exposures people typically experience in using pyrethrum based products.

Effect on the Environment:
Fate in water: Pyrethrum compounds are broken down in water to nontoxic products.10

Soil persistence: Soil application studies of pyrethrum showed a half life of only 1-2 hours.10 when used indoors, pyrethrum can persist much longer; up to two months or more in carpet dust.11

Wild life: Pyrethrum is extremely toxic to fish such as bluegill and lake trout, while it is slightly or moderately toxic to bird species, such as mallards and bobwhite quail. Natural pyrethrins are highly fat soluble, but are easily metabolized and thus do not accumulate in the body. Because pyrethrin-I and pyrethrin-II have multiple sites in their structures that can be readily attacked in biological systems, it is unlikely that they will concentrate in the food chain.12

Effect on beneficial arthropods: Synthetic pyrethroids are broad spectrum insecticides and are notorious for killing and repelling beneficial arthropods. However, since pyrethrum residues on the plant break down quickly, the effect on natural enemies is reduced. Pyrethrum is highly toxic to bees. The average lethal dose (LD50) for honeybees was measured at .022 micrograms per bee.13Direct hits on honeybees and beneficial wasps are likely to be lethal.13

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