Many people are concerned about using disposables part time in case the chemicals used to produce them are detrimental to the health of their child. Rest assured, they are not. Here is a collection of information from various studies.
Safety Evaluation Of Superabsorbent Baby Diapers (P&G) 
Superabsorbent disposable baby diapers are sophisticated, well-engineered products that provide many benefits including convenience, comfort, exceptional leakage protection, improved hygiene and skin care benefits compared with cloth diapers. Safety assurance is an integral part of the diaper development process at Procter & Gamble, with the goal of ensuring safety for both caregivers and babies. A systematic, stepwise approach to safety assessment starts with a thorough evaluation of new design features and materials, using the principles of general risk assessment including, as appropriate, controlled trials to assess clinical endpoints or independent scientific review of safety data. The majority of the diaper materials are polymers that are safe and do not have inherent toxicity issues. Trace amounts of non-polymeric materials, such as colorants, are assessed based on their skin contact potential. New materials or design features are introduced in marketed products only if they have been shown to be safe under the conditions of recommended or foreseeable use. The product safety continues to be confirmed after launch by means of in-market monitoring. This article provides a broad overview of human safety exposure-based risk assessment used at Procter & Gamble for absorbent hygiene products.
‘The topsheet is the layer in direct contact with the baby’s skin. It consists of a soft nonwoven synthetic sheet, composed of polypropylene/ polyethylene, either alone or as a blend.
The acquisition/distribution layer is usually composed of a modified cellulose patch and a polyester-based layer sandwiched between the topsheet and the core, which is not in direct contact with the skin.
The absorbent core is the inner-most layer of the diaper. It typically consists of a blend of polyacrylate granules blended with fluff cellulose pulp (bleached by an elemental chlorine-free process) and encapsulated by either a cellulose or polypropylene nonwoven layer.
Materials used in diapers are mainly of polymeric nature. These materials are safe and no inherent toxicity issues are associated. However as for any product, there will be low levels of non-polymeric components that may be introduced into the product for example from process aids used in the making process, or they could be aesthetic ingredients such as colorants or scents that are added at low levels. To provide a high level of safety assurance we focus on the assessment of such substances prior to consumer studies or widespread human exposure in the marketplace.
A key principle for diaper exposure assessments is the fact that disposable diapers are a solid product based primarily on solid and inert polymeric materials. Thus, the majority of chemicals are of limited concern since they are large polymers which are usually inert and not absorbed through the skin (Krause et al., 2006). The remaining substances for further evaluation are the non-polymeric ones. For relevant exposure to the skin, these ingredients must be released from the polymer and migrate to the surface of the diaper to be available for dermal exposure. An assessment of this release and migration from the polymer is important in order to obtain a realistic exposure estimate. When no data are available, a conservative default value of 100% migration of the free fraction is typically assumed.
Another step in the risk assessment process is known as hazard identification. It is the phase during which a toxicologist evaluates the inherent toxicity of a chemical to identify whether it can cause an adverse health effect given the relevant route of exposure.
As outlined previously, the majority of materials used in diapers are large polymers which are chemically inert. They do not penetrate the skin and therefore, are of negligible concern. Special attention is given to trace level, non-polymeric substances like process aids, aesthetic ingredients such as colorants or scents or potential levels of monomers, solvents, and additives used in polymerization reactions or syntheses. Understanding the chemistry of the substance is often helpful in this regard. The exact source must be considered, as different purity grades may be available and different suppliers may provide material with different impurity profiles. The full complement of hazard identification information can be drawn from several sources, including data from toxicity testing, evaluation of chemical structure to identify structural alerts, and data from human experience.
The initial analysis of a substance focuses on the evaluation of those physico-chemical parameters such as molecular weight and solubility which help the assessor to predict for its likelihood to migrate out of the diaper and be available for skin exposure or even to be bioavailable via skin permeation. Should there be any evidence for skin exposure or bioavailability, the chemical is further screened for alerts of concern using a tiered approach.
It should be noted that there is insufficient scientific rationale to apply any additional infant uncertainty factor for higher susceptibility of infant skin (SCCNFP, 2002; Renwick et al., 2000). Structural and functional skin barrier properties have been shown to be equal between full term neonates, infants and adults. Several studies and observations support the conclusion that newborns and young infants are even less susceptible to skin sensitization owing to an immature or developing immune system, respectively. This position is supported by several pieces of information related to epidermal skin biology:
1. Epidermal thickness, density of epidermal cell layers and cellular structure are identical between adults and newborns (Fact Book, 1996; Fairley and Rasmussen, 1983; Holbrook, 1982). The reduced thickness of neonatal skin relative to adult skin, particularly the dermis which has smaller collagen fibre bundles and immature elastic fibers (Rook et al., 1992), is irrelevant when considering the potential for induction or elicitation of a sensitization response since sensitization processes are initiated in the epidermis and not the dermis.
2. Full-term newborn infants have a functional stratum corneum and a mature skin barrier function equal to adults (Fact
Book, 1996; Kalia et al., 1998; Cunico et al., 1977; West et al., 1981) Importantly, structural and functional cellular constitution required to build up a mature stratum corneum is already present in the late pregnancy (Hammarlund and Sedin, 1979; Harpin and Rutter, 1983). Age-dependent studies have shown clear evidence that skin barrier remains virtually constant from infancy to late adulthood (Leveque et al., 1984; Ghadially et al., 1995).
3. In vivo as well as in vitro studies have shown that percutaneous absorption of chemicals is similar in infants and adults (Rasmussen, 1978; Wester and Maibach, 1982; McCormack et al.,1982).’
Scrotal Temperatures Do Not Differ Among Young Boys Wearing Disposable Or Reusable Diapers 
Results and Conclusions: In this study, we have clearly shown that scrotal temperatures are the same whether the child is wearing disposable or reusable cloth diapers with a protective cover. The only situation in which scrotal temperatures were found to be lower is when the cloth diaper is used alone without a protective cover but this is not representative of how these products are actually used. We also found that on average scrotal temperatures are significantly lower than core for each diaper type. Occasionally, we did see individuals in which the maximal scrotal temperatures approached core temperatures but in every case the thermal sensors were soiled by a bowel movement. We also found that skin surface temperatures increased not only when covered by a diaper but also due to the thermal insulation provided by outer garments and blankets.
Should We Rubbish Dispsable Nappies? An Assessment Of Common Claims Against Disposable Nappies 
‘Conclusions by NCASI, based on experimental work, a review of envirological data and other relevant information, indicate that there is little likelihood of dioxin migration from nappy fluff pulp to urine to baby skin (the postulated method of dioxin transfer) (NCASI 1987: 29). This is contrary to the claims made by Provost (no date) and (Rassaby 1990).
The low level of risk posed by disposables to infants is attributable to: dioxin having a very strong affinity for organic matter and thus limited potential of migration to a solution; analysis of possible mechanisms and rates of dermal absorption of dioxin; data on migration on soils and related compounds; a non pulp liner separating the pulp from the skin; and the amount of urine available to the skin being small (NCASI 1987: 56).
This risk is further reduced by: Kraft mills producing nappy pulp for the Australian market using 100% dioxin substitution; pulp mills continually improving and upgrading their environmental standards; and no detectable traces of organochlorines found in NZFP fluff pulp (no data was obtained on dioxin levels in USA pulp) (Johnsson 1993; Berry et al. 1992 and Balousek 1993). Nappies manufactured using the Magnefite process and bleached by peroxide steep bleaching do not contain organochlorines, as the bleaching process, uses no chlorine or chlorine containing chemicals. For the infant or baby, virtually safe concentrations of TCDD in nappy fluff pulp, corresponding to a 1 in a 1,000,000 life time cancer risk is 2,000,000 parts per trillion (NCASI 1987: 78).
However, serious nappy rash may increase absorption of TCDF (assuming it is present in the nappies) if no barrier creams such as zinc oxides are applied to prevent urine contacting the skin. This is based on evidence supplied by Ulsumar et al. (1978 in NCASI 1987: 61). With regard to lipophilic ointments such as vaseline, it is thought that dioxin (if present) is retained in the cream and therefore will not penetrate the skin (NCASI 1987: 44).
One of the concerns raised by Rassaby (1990: 28) is that babies’ skin is more sensitive than adult skin. Whether this claim is accurate or not is difficult to establish given: the small amount of research that has been undertaken which has compared chemical penetration through the skin at different ages; the very few studies that have specifically looked at newborn skin absorption; and the conflicting conclusions reached by different authors from what evidence there is (Fisher 1985: 213; Behl et al. 1985).
According to Behl et al. (1985), a number of studies suggest that there is a strong indication that infant skin is more permeable than adult skin. This view is in contrast to Fisher (1985: 221), who states that “it does appear that the barrier properties of the full term infant may be every bit as good as those of the adult with respect to at least some materials”.