Our ancient and spiritually strong sages (rishies) have given their own opinion about impurity in Hindu religious scriptures. Impurity has been described in two ways : at birth impurity and at death impurity. In regulating this impurity, the ancient sages must have kept in mind same scientific theories.

Dasham shàvmàshaucham sapindeshu vidhiyate|
Sapandità tu purushe saptame vinivartate||
Jananetyevamev syàt --- Manusmriti (5/59)

This impurity is decided by same gotra or same 'Pandita'.

Shudhayate Vipro dashàhen Dwadashàhen bhumipah|
Vaishyo panchadashàhen Shudra Màsen shudhayati |Manusmriti (4/83)

This means that a Brahamin can get purified in ten days, Kshatriya in Tweleve days, Vaishya in Fifteen days and Shudra in one month. Generally this is the rule. During these days one should not perform auspicious functions, devayagana, marriage and other rituals, bathing Gods and worship etc. One should mentally worship Gods.

If there is any miscarriage within four months of conception, mother remain impure for three days, whilst father till his bath. At the time of birth there is no impurity till cutting of baby chord, after that for ten days it is considered as impure. If child dies within six months the parents will observe it for three days. From six months to one year if the child dies then also parents will observe it for three days but other family members for one day. If a child dies at the age of three, and after the haircut ceremony (mundan Sansakar) one has to cremate the child. Smaller babies are buried or pushed in flowing water.

If married daughter dies at parents house then parents and/ or brothers will observe impurity for three days, while uncles only for one day and in-laws for full time as mentioned above. If grandfather (Nana) dies then grandson observes impurity for three days but if Grandmother (Nani) dies it is observed for two days. If grandson (Dohitra) dies then grandparents (nana- Nani) have to observe for three days but if it has taken place before 'Yagyopaveet' the it is observed for one day.

For sisters death it is one day and so for married girl. If mother- father in-laws die then son-in-law will observe it for three days but if they die at far distant place then observe for one and half days. Father's sisters, mothers's sister or any relations of father and mother die then observe for three days.

To regulate and decide for impurity our scriptures have given clear directions in Dharam sindhu, Nirn.ya Sindhu, Vrat Parichya, Vrat raj, Tithi Nirn.ya. Please look for these books for more details.