One of the most important concerns for public health related to toxic elements is exposure to Lead (Pb). By now there is no evidence that Pb has any benefit or an essential role for humans. On the contrary, several studies have demonstrated that there is no safe threshold of exposure, especially for children. On the other hand, Manganese (Mn) is an essential element for humans. It works as a cofactor for a variety of enzymes, therefore, is a crucial nutrient.
Our experiment was organized to increase the understanding, by exposure of mice in vivo, of the behavior for co-exposure to Pb and Mn. Shortly, four groups of mother were divided into: control, Pb exposure, Mn exposure, and Pb + Mn exposure groups respectively. The exposure via was done through drinking water and Pb solution had a 100 ppm concentration and Mn solution had 2 g/L concentration. Exposure begins 5 weeks before the delivery.
Then the offspring were grouped according to the mother exposure group, and the sub-grouped until they reach the ages of 0 –3 (0-3 PND), 14 –18 (18 PND), and 60 (60 PND) post-natal days respectively.
During this period the groups 18 PND and 60 PND continue the exposure via lactation. The exposure continues, until the sacrifice, for the through lactation until the 21 days after born. When every group reach the need its age, they were sacrificed and the blood samples, among others, were taken for analyse the element concentrations.
The metal concentration analysis for the blood samples was performed using ICP-MS. Briefly, the samples were digested using ultrapure HNO₃ at 80 °C, from it the analytical solution was prepared. As quality control were used CCL® and SERONORM® Level 1 and 2. The full procedure is reported elsewhere.
The principal statistic for the concentrations are presented in the Tables 1 and 2.

Table 1. Pb concentrations in ppb (µg/L)

Offspring´s age	Exposure group
	1 Control			2 Pb exposure			3 Mn exposure			4 Pb + Mn coex
	n	x̄	sd	n	x̄	sd	n	x̄	sd	n	x̄	sd
0-3 PND	11	2.68	2.11	7	280.81	149.15	17	2.86	4.14	30	178.98	69.55
18 PND	18	2.80	1.41	17	341.16	107.99	17	3.49	1.04	54	249.88	71.00
60 PND	18	1.56	2.35	18	9.33	3.09	20	1.12	0.58	42	3.70	2.05

Table 2. Mn concentrations in ppb (µg/L)

Offspring´s age	Exposure group
	1 Control			2 Pb exposure			3 Mn exposure			4 Pb + Mn coex
	n	x̄	sd	n	x̄	sd	n	x̄	sd	n	x̄	sd
0-3 PND	11	37.10	55.36	7	80.26	136.19	17	134.61	119.28	30	262.66	429.80
18 PND	18	11.77	2.05	17	15.57	5.24	17	63.52	33.52	54	87.07	43.31
60 PND	18	11.42	3.65	18	9.33	3.09	20	10.85	3.92	42	10.1	3.24

Here the control groups were expected to show the lower concentration, base line, for each mice age group. The lower values for Pb and Mn correspond to the age PND (60) with an average of 1.56 ± 2.35 ppb and 11.42 ± 3.65 ppb for Pb and Mn respectably. On the other hand, the higher values for Pb correspond to “Pb exposure” group at the age of 18 PND. This due probably to the constant exposure of the subjects from the maternal womb until the end of their life. The value found for Pb corresponds to 341.16 ± 107.16 ppb. Nevertheless, for the Mn concentrations, the higher values were presented for the “Pb + Mn coex” at the age of 0-3 PND, with an average value of 262.66 ± 429.80 ppb.
A comparison between the values got to Pb “Pb exposure” and “Pb + Mn coex” show that the presence of Mn have inhibitory effect in the absorption of Pb for the subject. Meanwhile the behavior for the Mn seems to work at contrary. When the groups “Mn + exposure” and “Pb + M coex” are compared the amount of Mn seems to increase when Pb is present. This can reveal a tide relationship between the metabolism involving these metals.
Due to the exposure (single and co-exposure) is finished 20 days after the delivery, the age group of 60 PDN, seems to return to base values equal as the control group. In this way is possible to hypothesize that for exposure time of 20 days, a period of 40 days is enough to eliminated from the blood the excess of Pb and Mn. For a better understanding of the metabolism pathways of the storage organs, a set of samples from liver, bones, and brain were collected from the subjects and will be analysed to continue the study.